Halving tied notes without losing ties

I use that now, but thats 4 keypresses for one action, and theyre not the same every time (F5 – length of note – note key – Shift-9). Plus, i want the entire tied note to stay connected. And it gets more complicated when I’m using the mouse.
Hence the request for a single keystroke. I would like to simply divide a tie without thinking about it.
For example, with the selected note (note entry mode not necessary), press something like Alt-2 to divide the tie into 2, Alt-3 to divide into triplets, etc. Maybe Alt-1 would combine a tied note with the next, if the measure allows.