I’ve just finished transcribing a fairly long book of leadsheet arrangements into Dorico (I was using 2.1 - 2.2 came out just after I finished, which would have saved me a lot of time on Codas etc … never mind).
I had to do a lot of these rhythmic figures above the staff, which are pretty common in New Real Book-style leadsheet writing (see attachment). I was generally happy with how they came out, but the process I arrived at was pretty laborious. Create the figure in a slash voice, then select it and filter only notes so that you can adjust the slash position, then filter it again to only rests so that you can adjust the rest position, then put the whole thing in cue size with small slashes and hide the leger lines, then manually tweak the stems in the melody voice (which will default to either upstem or downstem depending on the voice you create, but which should ideally just follow single-voice stem rules beneath a figure like this).
There are various ways that could be made easier (like, for example, an option to force stems to behave as if there were only one voice), but the dream way of doing it would be to make it behave like an ossia. Select passage, select staff > add ossia above > enter notes > done. If only an ossia could be defined as having no lines (and maybe one or two other options to do with where and how chord symbols appear), it would be pretty much perfect as it is.