You can feed back on on redesign drafts on this ticket, or this forum thread. They are a bit outdated, as I have been working on ListenBrainz and other things in the meantime (while the MB React migration continues), but there should still be plenty to look at.
The proposed redesign is inspired by the most widely-used UI userscripts, as well as open tickets, so it should be an improvement - I would be surprised if there are any top editors who don’t use a lot of scripts (does anyone browse the site at 100% size?), so there is a case for improvement there.
In any case, feedback now, rather than cry later 