Thunderbird is extremely slow after the new UI update 115.4.2

[DontWantAccount]

I've got this big new update with new UI that simply doesn't work.

I do lot of operations over IMAP and the UI rendering is so extremely slow, that I'm unable to work with my mailboxes. Steps to reproduce, using IMAP, with config to mark as deleted and manual purge:

* Select 500 unread email messages.

* Delete them

* Purge the mailbox

It either takes very long, while rendering each message change back and fort, or completely freezes.

How do I downgrade and block further autoupdates?

[SLCompulsion]

I am now seeing that it is only slow in one account and only in the InBox. I've compacted. I delete the Global Database to re-index based on this: https://support.mozilla.org/en-US/kb/rebuilding-global-database