Hi @Shift3
Welcome to our forum!
Agree with simo-k.
As a workaround, for the email you replied to, CC yourself at the same time, and set the relevant rules, that is, if the email is from your own account, and you're in column CC, take the action of Move it to the specific folder.
However, this may lead to too many duplicate messages that take up space in your mailbox (exist both the sent folder and the specific folder) and you may need to clean up the mailbox regularly.
Please kindly understand that many functions are not designed at present. To get this feature more quickly, I have found a post in feedback collection website, and you could vote for it. Many features of our current products are designed and upgraded based on customers’ feedback. You can also make suggestions on that website and hope Microsoft will notice this in the future.

Thanks for your support and understanding!
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