Issue 1:
Because you request it in the console, I will post this exception here.

Performing hot reload...
I/flutter ( 5553): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 5553): The following assertion was thrown building SlideTransition(animation: AnimationController#634b8(⏭
I/flutter ( 5553): 1.000; paused; for MaterialPageRoute<dynamic>(/))➩ProxyAnimation➩Cubic(0.40, 0.00, 0.20,
I/flutter ( 5553): 1.00)➩Tween<Offset>(Offset(0.0, 0.3) → Offset(0.0, 0.0))➩Offset(0.0, 0.0), state:
I/flutter ( 5553): _AnimatedState#de5ac):
I/flutter ( 5553): 'package:flutter/src/widgets/framework.dart': Failed assertion: line 4647 pos 12: 'child == _child':
I/flutter ( 5553): is not true.
I/flutter ( 5553):
I/flutter ( 5553): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter ( 5553): more information in this error message to help you determine and fix the underlying cause.
I/flutter ( 5553): In either case, please report this assertion by filing a bug on GitHub:
I/flutter ( 5553): https://github.com/flutter/flutter/issues/new
I/flutter ( 5553):
I/flutter ( 5553): When the exception was thrown, this was the stack:
I/flutter ( 5553): #2 SingleChildRenderObjectElement.forgetChild (package:flutter/src/widgets/framework.dart)
I/flutter ( 5553): #3 Element._retakeInactiveElement (package:flutter/src/widgets/framework.dart:2868:14)
I/flutter ( 5553): #4 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2895:32)
I/flutter ( 5553): #5 Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 5553): #6 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4654:14)
I/flutter ( 5553): #7 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 5553): #8 Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 5553): #9 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4654:14)
I/flutter ( 5553): #10 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 5553): #11 Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 5553): #12 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4654:14)
I/flutter ( 5553): #13 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 5553): #14 Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 5553): #15 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #16 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #17 StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 5553): #18 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #19 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #20 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #21 StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 5553): #22 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #23 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #24 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #25 StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 5553): #26 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #27 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 5553): #28 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #29 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #30 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #31 ProxyElement.update (package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 5553): #32 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #33 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 5553): #34 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #35 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #36 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #37 StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 5553): #38 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #39 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #40 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #41 StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 5553): #42 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #43 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 5553): #44 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #45 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #46 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #47 ProxyElement.update (package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 5553): #48 Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 5553): #49 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 5553): #50 Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 5553): #51 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2242:33)
I/flutter ( 5553): #52 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:626:20)
I/flutter ( 5553): #53 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter ( 5553): #54 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter ( 5553): #55 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter ( 5553): #56 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:751:7)
I/flutter ( 5553): #58 _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382:19)
I/flutter ( 5553): #59 _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416:5)
I/flutter ( 5553): #60 _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
I/flutter ( 5553): (elided 3 frames from class _AssertionError and package dart:async)
I/flutter ( 5553): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 5553): Another exception was thrown: 'package:flutter/src/rendering/box.dart': Failed assertion: line 1457 pos 18: 'debugDoingThisResize || debugDoingThisLayout ||
I/flutter ( 5553): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#79ad8 NEEDS-PAINT DETACHED
I/flutter ( 5553): Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#c070b NEEDS-PAINT DETACHED
I/flutter ( 5553): Another exception was thrown: RenderBox was not laid out: RenderOffstage#d09f6 NEEDS-PAINT
I/flutter ( 5553): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#79ad8 NEEDS-PAINT DETACHED
I/flutter ( 5553): Another exception was thrown: Duplicate GlobalKey detected in widget tree.
Reloaded 0 of 389 libraries in 293ms.

Issue 2:
I'm looking to set up some high-level navigation between some different pages of the Leafy app from our app drawer. The desired flow is as follows:

Page1 --> drawer --> Selection between {Page1, Page2, Page3} --> drawer --> Selection between ...

This would be much easier to do if the replace methods from NavigatorState were exposed statically through Navigator, just like the pop and push methods are.