It already exists (or you just added it)!
Ctrl-O = timestamp.
I also find:
Ctrl-T = Tag
Ctrl-P = Persontag
Rest is common Windows hotkeys (like Ctrl-S, Z, C, V, B, I, U).
That's all good. Thx.
(Maybe add a help list of hotkeys somewhere or add the information about the Ctrl-O hotkey to the timestamp icon in the top menu. )