I had to use the tempo popover today, and was a little confused about how to do tempo ranges initially, until I found something searching the forums.
In the popover I typed: q=70-80
It produced a very weird output. And caused me to do some forum searching.
My suggestion is with everything that is already so intuitive with Dorico, the method to add a tempo range really stands out as an unintuitive. Maybe it is me, maybe it is the program itself, but in the properties panel, I still was confused initially because tempo range was pre-filled in with 1000.000.
I would ask that later down the road, this be re-examined to make it as intuitive as the rest of the program.