First of all: Fantastic project, should receive more love from the community! :)

Just wanted to leave this ticket as an improvement I might work on..

Some very handy keystrokes are missing:

• for zooming (Ctrl+Alt/Cmd+Mousewheel/Touchpad)
• duplication Cmd/Ctrl+D (copy & paste combined, same position + offset of 50px top,left)
• Shift + KeyUp / KeyDown / KeyRight / KeyLeft should increase the speed of moving around to 10x the speed; holding the key should repeat the move operation in the direction of choice
• Shift + Clicking an element which has not been selected already should add it to the group of selection or create a selection if non exists yet. This use case is very common when you already selected a group of element via Rect-select but then want to add an element to this selection which is outside of the rect region.

edit: Removed grouping, as it worked when I checked again.
edit2: Added move speed multiplier
edit3: Added select multiple elements via shift keystroke