Manipulate selected files in Edit Index

I want to be able to click on clips in the edit index and add a flag, clip color, or some other way to quickly grab and organize those clips.

Yes, the Edit page implementation of the Edit Index is frustratingly limited in scope... for what it's worth though, unless or until the powers that be get their act together on this, you can use the Fairlight page Edit Index to facilitate what you want to do.