I've tested the v-0.5.
It's work as You say.
1.In searchable mod all's well, it work correct.
2.In Category list remain previously symptoms and the most important is on popup preview over furniture are show only the first in row.
3.It appear the delay are drastically reduced as I can't mention to see.
4.

9. After enable group view can't return to standard view

Indeed but accessing the Settings button and change the view from one to another resolve this (at the moment).
While I must go to Settings to switch between mod of view I remain on opinion to be there a check box for enable the Grouper.
5.About perimeter now is OK with short info (only P=xxx.xx cm).
In this mod is really useful.
The full information are not necessarily to show but for future "Room Walls area" which will be show near or under P=... [:">]

PS

Because i write this plugin only in my free time

I really appreciate this [=D>] and sorry if some times I demand too much.
So, please keep working ONLY You have time and have a good disposition for this.
Thanks again for Your work!