The first notation program that I ever used, Mozart the Music Processor, had a nifty little feature where you could select a note, and then using a simple key combination break up that note into smaller values. For example, a half note into four eighth notes. I imagine something like that in Dorico: select half note A, press command (or some other key) + 5, and presto, 4 eighth notes A. Would come in very handy if you want to add embellishments to a basic harmonic framework, for example.
Select half note
Press ‘r’ 3 times
Dorico already has the U key.
Put the caret wherever you want to split a note, then hit U.