Control-S lets you search a string in the signature. 14.4 File editor You can edit files with it, if you're not yet used to emacs. Otherwise you can use it as a browser, making occasional corrections. For this last option, you may choose the shell via a dialog. Essential functions are in the Compiler menu.
Preferences opens a dialog to set internals of the editor and type-checker.
Lex adds colors according to lexical categories. Typecheck verifies typing, and memorizes to let one see an expression's type by double-clicking on it. This is also valid for interfaces. If an error occurs, the part of the interface preceding the error is computed. After typechecking, pressing the right button pops up a menu giving the type of the pointed expression, and eventually allowing to follow some links.