The tooltip will be fixed in the final version of GrandVJ 1.5
As the feature set is now fixed for this version, we won't change the way the transitions work in GrandVJ 1.5.
However, if you give me some detailed examples about how this feature could be used in Mixer mode, we could think about improving it in a next version.
Essentially, the way transitions would fit best into my own personal workflow would be to be able to specify a transition for individual clips, then have those transitions executed when the layer play/stop toggle is used (maybe if the layer is set to A/B this transition is overrided). Like how they work in synth mode essentially. For me ideally I'd like synth and mixer mode to be combined, I'd like the flexibility of being able to use methods from both.