"Transition" vs "Mix Clips" and reorganize Compositions
The first time I clicked on Mix Clips I said: "Here is a transition." Because this tool makes the passage from a clip to another. Then I don't understand why you chose another term. What are Mix Clips? Yes, maybe a transition but also a blend, alpha strobing, or morphing... It's not clear. To avoid the word "Transition" in a video editing software is not a good idea.
And I also suggest to separate the tab Compositions and its selection box (picture below) in two categories: Transition mode (Cairo Affine Bland, Cairo Blend, Composite, Composite and transform, Dissolve, Luma, Regionalize, Slide, Transform and Wipe) and Blending mode (the rest). Again, for more clarity.