Apparently, we can’t add effects to folders.
I don’t think it has to do with bugs; I think they don’t know how it’d work.
But I have an idea!
When you put an effect on a clip, all instances of the clip get that effect.
So if you add an effect to a folder, all the clips inside, as well as its subfolders, take on the effect.
Example:
If I add an effect to image.png, then all its instances are given the effect as well.
sackboy_disgust.mp4 is unaffected.
But adding an effect to global will affect both image.png and sackboy_disgust.mp4.
If you take any of those files out of global, then the effects will disappear.