Temporary Tempo change for recording in realtime Dorico for ipad

Is there a quick way to set a metronome tempo to aid inputting midi in real-time without having to write it on the score and then change it back again?

Yes. In the upper right corner there is the Fixed Tempo Mode display. Tap the note to switch between tempos as written in the score and a fixed tempo you can set (quarter note BPM). Tap the number to change the speed. See the User Guide for details.