Rehearsal letters visible when instrument filter is in use

Greetings! When using the instrument filter I find that the rehearsal letters are hidden unless the top instrument of the score is included. Is there a button somewhere I have neglected to push?

Dorico v6 for iPad

There was a thread about that not long ago, but I can’t find it.
You can check Library->Layout Options->Staves and Systems->System-attached Items, and perhaps the Specific Players.

Jesper