I think it would be helpful if the retake action could take into account multiple selections. For example when there are a few bars where the pedal has retakes every 2 beats it could be faster to place a long pedal, then select the notes where the retake happens and click the retake pedal marking instead of going to and fro between the score and the panel.
Yes, I agree it would be helpful to be able to add multiple retakes in a single command. This is something that is on our list for future improvement. You can do it more quickly than you are presently doing it, though: select the note or rest at which you want the retake to appear, then type Shift+P for the playing technique popover, and enter ^ then hit Return.