Compose doesn’t support adding arbitrary semantics nodes that aren’t tied to compose nodes. You’d need to use the compose layout system to place each of your boxes.
You could do this in a couple ways:
1. Split up your drawing code so each of the boxes draws itself. I would recommend this unless your drawing is too complex, in which case you could
2. Place compose nodes that don’t draw anything over your canvas, in the same places and sizes as the boxes on your canvas.