How to handle appropriate UI controls separate from "playable" area
I've been playing around with some basic Godot things. Reading/writing files, basic mouse input, basic GUI, etc. Primarily this has been to give me a little familiarity with Godot and GDScript without worrying too much about assets, resources and things but just focusing on a couple very basic aspects.
One question I've been dealing with is how to structure a UI where there is a section of command items (say a toolbar at the top) that would allow you to save, load, or clear items on the screen for example and then an area that accepts mouse input to draw lines or circles. The save/load functionality stores that and reads it back.
How would this be structured? Would the area accepting mouse inputs (draw a line when button is pressed) be a separate viewport for example? I've tried to set this up and visually it looks OK but behind the scenes my input handler draws another line when a toolbar button is pressed and I want this to only occur on the main drawing area.
I feel I'm having trouble expressing this question well. I'm happy to clarify if I can.
This question here is certainly similar and any answer may be related: