Collage of my thoughts on the "Held Quasimode" interface pattern (AKA the body holds the state).
From interfacelineage.com/quasimodes-h...

The one place I'm still unhappy with my current setup on the canvas is draw mode. Where drawing is a completely separate latch mode. I can imagine a "press to activate" draw mode working, but the real issue would be how I group together strokes. Right now exit serves as signal for what to group.
Maybe time and proximity thresholds would be enough...