Shortcuts

Key	Action
Ctrl+N / Ctrl+O	new / open
Ctrl+S / Ctrl+Shift+S	save / save as
Alt+G (or Ctrl+R)	render and play
Ctrl+T / Ctrl+D	new section / duplicate section
Ctrl+B or Super+N / Ctrl+Shift+D	new bar / duplicate bar
Super+Delete	delete the selected bar
F9 / Shift+F9	show / hide the section list / the settings column
Enter (in a bar)	go to the next bar (creates it if needed)
Space / B / S / L	play-pause / from the start / stop / loop
F1	guide
Ctrl+Q	quit

Space, B, S and L work when you are not typing in a field: so you can type Bb or Dsus4 without trouble.

Built-in guide

Help ▸ Guide (F1) explains every part of the window: Start, Song, Sections, Chords, Key, Scales, Player and Keys.