This may be in the pipeline already - I would find it more streamlined if rhythmic feel were a property of the tempo marking rather than a separate element. As it is, I find it unwieldy to work with rhythmic feels, as they often coincide with a tempo marking.
The other thing I would like to see is the ability to specify the type of tempo marking (i.e. absolute/relative/reset), either via a property or through the popover (or both).
And finally, when selecting, say, “mosso”, in the relative tempo change, I would expect “piu” and “meno” to adjust the percentage to be higher and lower than 100% respectively, but currently it seems that “mosso” is always 110%.