(individual instances, that is) …so that you can turn all of them off/on with a single button!
Reason: I like overusing effects that are CPU-heavy and make the sound “thicker”, but are not strictly necessary for composing. Yet some of them are (often those use very little CPU), so when I switch to “only internal effects” it’s not possible to compose in a meaniningful way most of the time. It’s possible to work around it by turning off tracks and taking notes of what to take a look at when listening to the rendered song, but I imagine such a feature could make that unnecessary in 9 out of 10 cases.