Filters are run automatically on the Inbox when getting new messages, but you could make a filter like the one in the attached picture, to act on unread messages less than a day old. It might be necessary to add extra rules to restrict the filter to certain senders or subjects.

Thanks for this reply, and sorry for my late reply.

Just to think outside the box, is it possible, that when an email is marked as read, that the filter is applied too? With the result that when an email is marked as read (manual and automatically after reading) that the very same email is filtered accordingly?

No, filters only run automatically according to the options in the filter window, i.e. when getting new mail, or archiving, or after sending, periodically etc.

Thanks, but that is not my question.

My question is not about what is, but about is it possible/to request a new feature. Namely to sort emails direclty after reading.

Now the new emails become just emails /unbolded and stays in the inbox/folder.

I am interested if it is technical possible/I request a new feature, as the emails become unbolded, that they also get filtered? To run the filters as the emails get unbolded?

To put it differently, how does Thunderbird that you have read a unread email? Use that recognition as a trigger to filter that specific email too.

Thus: Now: New email > read > email (unbold) Request: New email > read > email (unbold) AND filtered

Submit a Request for Enhancement report on Bugzilla.

Thanks.

But I think someone have it already done. After a recent update, a read email will be moved to the appropriate folder after a few minutes by Thunderbird itself. Just how I have set the settings.