After each update settings get lost.
I am not talking about the custom jobs, but hte WPforo settings,
like max attachment size.
Is there a way to export settings and import after each update?
Please don't say "After each update settings get lost". This is too far from truth. If you have faced a few time of a few option change, it doesn't mean we always change all settings in each update. This is not true and wpForo settings stay intact with each update.
We don't change any settings on update, unless it's modified to other processing types like the attachments Max Size from MB to B. This was changed to allow people set smaller Max Uploaded Sizes. So this is not an accidental change this is planned change and it should automatically recount your MB to B so the result should be the same. If somehow the automatic re-counting was not correct for you, you can do that manually:
1 MB = 1048576 B
1 KB = 1024 B