I have a player that has Vibraphone, Suspended Cymbal, and Electric Guitar instruments. On the Full Score layout of this piece, with the “Fretted Instruments” layout setting set to “Notation Only”, everything appears as I expect in the score: the instrument changes are shone, and there is only 1 staff shown in the score/page view (while the usual 3 staves are shown in Galley View). However, when I switch to “Notation and tablature”, suddenly all three staves for each instrument are shown throughout the entire piece in the finalized score and Page View. The individual part layout for this player seems to be fine (shows 1 staff appropriately), but the Score does not.
What I expected to happen, was that 1 staff would be shown throughout the entire piece as normal, and when it came time to switch to Electric Guitar, the notation and tablature would be shown (again, without the vibraphone and suspended cymbal staves showing, and certainly not all of them shown throughout the entire piece).
I took a look at your file and I found an explanation.
The reason why the Part seems to work is that you are hiding empty staves in the part layout. If you deactivate that, you’ll note that the instrument changes are not working either. Also, there are no appropriate “to Instrument X” texts visible in the part, which shows that the instrument changes are actually not working properly, too.
It seems that as soon as tablature is involved, instrument changes work in no layout. Or to put it in another way: you’ll need to hide empty staves in the full score, too. If you don’t want that, you should be able to achieve what you want with manual staff visibility.
That is unfortunate that tablature breaks the normal instrument change functionality. I will work around the issue by hiding empty staves in the full score, and then excluding every player/section from that setting except for the Vibraphone/Electric Guitar part. That leaves one remaining issue: on pages where instrument changes occur for that player, the staves of both instruments will still be visible, and there is no indication via bracketing, etc. that both instruments belong to the same player.