That's a relief! I revisted Uwe's videos and the lack of volume control appears to be in the tremolo settings. You can set the amount of tremolo but not the volume of the tremolo, which I guess is the volume difference between the main reed (in tune) and the offset reed (slightly higher or lower).
So that's one worry resolved! I'm getting more and more exited at hopefully being able to try a Fisa in person, hopefully at WMF2025.
The Fisa has to do really well to replace (or just complement0 the accordions I already have. I consider all the orchestral sounds, drums and other features just "nice to have" but for me what's really essential is whether it can replace 1) a nice classical accordion with cassotto and 2) my bass accordion (which needs to sound like an accordion, but very low, going down to C1).