Please consider adding font size as a text formatting option. The pre-formatted headings are quite inconsistent, with some text options making the text too small or too thick.

I can't copy plain text to all emails going to customer (the reminder and so on).
And in a new booking slot I am limited to a short amount of text. I can't save this email text i I go over e.g. ten sentences.

I need also e. g. 20 min or 3h or longer slots. Please leave the timeslots open to configure our own length.