Thanks for filing this idea. And thanks Ariel for explanation.

I'll close this idea then accordingly.

This exists, if I understand the request correctly. In Level Manager with the Symbology drop-down set to "Overrides", right-click on the list header row (the area that says Name and has the color, linestyle, lineweight, "Used", etc.). In the menu that pops up, you can toggle on Transparency and other settings. Once they're toggled on, those settings can be controlled with overrides.