Time marker adjustments

At the moment, I find it really hard to see if an appointment ends at 11:30, 11:45 or 11:55. Right now I am kind of guessing when an appointment has finished and if I can offer the 11:45 slot or if I should offer 12:00 instead. When I then click to book it it becomes more clearer, but at this point I have already proposed a time that I then need to go back on immediately.

I would like the option to turn on a feature that divides every hour in 4 blocks of 15, and for every block to be marked as “11:30, 11:45 or 12:00”