keyboard shortcuts are already documented in deltachat-desktop/KEYBINDINGS.md at master · deltachat/deltachat-desktop · GitHub, but that is impossible to find for normal users.
So I propose an inApp keybindings cheatsheet accessible from the Help menu and via common keyboard shortcut.
for reference: discord already has sth. like that:
This addition would make the knowledge about the keyboard shortcuts more accessible for users of deltachat desktop.