Master effect as a clip
The disadvantage of putting it into master effect is that it works in general and not clip based.
Introduce Master effect working as clip (like an "adjustment layer" in Premiere) could solve the problem. This would be a special type of clip which works like the master effect. "Adjustment layer" can contain/host effects, group effect or other clips. If the "Adjustment layer" behaves like a clip we can adjust depends on which track level and how long the "adjustment layer" is.
If integrated in the timeline ruler it should work in multiple zones.
Edited by Eugen Mohr