dear musicmaven,
thank you for taking the time for the very well understandable explanations. I will give it another try later in the day, when I have time.
musicmaven, I spent some time again today on this.
I deleted the intonation frames MM and added local music frames. Here it is called LL 1. I get it to display the music I want:
But now again, when I remove the Master Page overrides at the end, I will have the music there back in MA:
End of Score, no page overrides:
When I untick these extra flows in Setup Menu also the local frames LL disappear in the score.
My question: I could completely erase the Intonation flows.
If I then create local flows, I can choose a player/system - but I can not choose a flow to input the necessary music. Very tricky to solve this, I feel.
[edit: I will re-read Marcs last message and try to duplicate his route]
Dear k_b,
I think the only problem in your last attempt is that you unticked the extra flows at the wrong place.
If I understand you well, you unticked those in Setup mode— which makes them completely disappear from the Layout. I suggested you untick them in the masterpage editor (double-click a masterpage in Engrave mode, right-down panel), in the third column of the music frame property — see my picture attached in my post, it’s named FLOWS:…
This way, your extraflows are not in the Main musical chain anymore, but still exist in the Layout.
Hope it helps!
Thanks Marc,
I opened the “First” Master Page in the master Page Editor, actually I had to tick all flows except the two ones I did not want (this was automatically mirrored from left to Right) and closed the Master Page Editor.
Voila, everything as wished - this was very easy indeed 
It did not need more than that, these changes were also reflected in the “Default” Master Page and in the others I had created.
The two “omitted” flows are still accessible in Galley view, so I can make edits there or even directly in the local music frames on the relevant pages.
[Solved]
Great news
yes, thank you for your help (and patience).