Dear VM
I can report that the system, after return to the previous UI layout and a bit of time, seem to work as well as it worked before. The web changes (block/unblock) and switches for the themes are retained, work well, and are applied fast. I haven't tried more extensive lists of sites yet.
Thank you! Please keep this layout - it's just fine (previous an "improved" one, even if it worked well, looked less practical than this the current "old" one)!
Regards