These suggestions can help a lot, while the suggestions themselves not really being that big

*Bring back the Remix Tree: I know you can just put https://scratch.mit.edu/projects/projectid/remixtree/ into the url, but some scratchers don't know that. The Remix Tree was, and still is, a great way to see the different remixes of a project quickly, and adding the button back on the project page would be a great re-addition!

*A few audio options: The next few points are just things that could help audio
*Highlighting certain parts of an audio file: This is important if any of my other audio suggestions, since they require the need to highlight certain parts of an audio file to be added
*Deleting certain parts of an audio file: What I mean by that is that in Scratch 2.0, you could just highlight a part of an audio file and delete that part (Including deleting the middle of the audio, which Scratch 3.0 can't do). This is a small suggestion that could improve Scratch project design in many ways!
*Fade in and Fade out audio effects: I mean, they can add atmosphere into some music, so why not?

*More transparency options on costumes: What I mean by that is that some one could open the color menu in the costume section of the editor and change the opacity of the color without having it fading in at one part and out at another. This could greatly improve costume editing and increases Scratch's potential

These are just suggestions. They can help make Scratch 3.0 less disliked in the Scratch community. If someone at the Scratch Team is reading this, than thank you for at least reading my suggestions!

The scratch team already is working on all of the audio suggestions you mentioned (or else, they'll start working on them soon—they said they would come a few months after the initial release of scratch 3.0)