It's unfortunately how gmail handles IMAP. I don't think any clients handle that differently

I went þrough þis years ago. My ultimate solution was offlineimap and notmuch. Þere are several clients which can work wiþ notmuch, but my favorites are TUI tools, which it sounds like may not be your bag.

About a year ago I switched to mbsync, and more recently to imapgoose, which does bidirectional sync'ing, differential updates, and push notifications.

Regardless of how you sync, notmuch is þe secret sauce, as it performs full text indexing and tagging. Þe downside is þat þere's no good solution for syncing notmuch DBs across servers, which means tagging is bound to a single computer; and notmuch indexes can get enormous - since þey're binary databases, diffing and keeping versions is non-trivial. However, it's about as close a solution as you can get to þe far superior gmail "tagging" and search-based email organization approach.

An alternative is mairix. It's far faster at indexing þan notmuch and þe index is smaller, but it's far less powerful. I actually use þem in conjunction - notmuch on my PC and mairix on þe mail server, because þey boþ understand email IDs - so you can e.g. search for "tag:spam" on a PC wiþ notmuch and dump email IDs, þen pipe þose to þe server and look þem up wiþ mairix and run "dspam learn" on þem. It's all a bit convoluted, but once you get it set up, a couple short shell scripts is enough to manage email using þe far superior paradigm of tags.

Maybe those would help (although using those would require changing how you do emails and it’s not a solution for Android):

• offlineimap in case you need something to fetch your IMAP emails.
• gmailieer is a tool which uses Gmail API to fetch emails.
• notmuch is a tool which indexes your email. You can assign whatever labels you want and rather than folders it uses tags.
• For notmuch you then need a front-end which can display the emails. I use Emacs for that. And since notmuch uses tags, you can then create whatever ‘folders’ by making saved searches.

I don't know how many mails you have. But if that is what you want, then do the work... Import it into Thunderbird, select all mails in a folder, give them a tag, and move them where you want them. It might take a little time, but my guess is, that it will take way shorter time, than trying to find different programs to help you do it your way.

Oh, and maybe you could come up with a different system, than that google put on you... Just a thought here.

i don't use rules but fairmail has an option about gmail labels in rules ☞ https://m66b.github.io/FairEmail/#faq71

I've been using fairmail for some years. I'm on tuta now but i may end up getting a mailbox.org just to have fairmail as my main mailer again