gui bug fixes & feature requests

[44467699] When users drag and drop onto a [filled singleton] slot, it should call replace. Currently it calls add. 
[44955765] Stop giving a dialog  box for every error, instead, output to python console.
[44474077] Can't edit and save changes to file imported through GUI text editor
[44542337] Users should see related tabs in the editor windows show up next to each other and in a specific order
[39063129] watchdog error
[XXXXXXXX] Add 'Save a Copy' option to file tree context menu