When a developer saves changes on a layout, AND that layout contains a slide control, then all users who have that layout active will see a reset of their slide control: it jumps to the first slide.
Is there a way to prevent this OR:
Is there a way to trigger this and let a script activate the original slide.
Couldn't find a trigger that reacts on this "developer-layout-save-event", that's why I post my problem here.
The solution is “don’t do that”.
When you make changes to the layout FMP has to reload the layout and it uses the default view options.
Thanks, Malcolm,
I can't prevent working in active layouts and it is just a small annoyance for the users but I thought someone had a workaround.
Be extremely careful. A small visual refresh may be inconvenient but bad things can happen too.
This touches the already many times discussed topic about working on a live database or transferring the data to a new version. In this case (and many other cases imo) it is necessary, especially for smaller corrections but sometimes also for larger.
I will very carefully click the OK-button... 
I avoid working on life databases. However, if necessary, it is done when all others went to sleep.