Permanently flagging messages

Is there a way, without changing a message’s tag, to permanently mark it as important, like enabling a star next to a message in Thunderbird? I can flag a message in eM Client, but that seems only to be temporary. I’m looking for a way to mark a message as one that I must keep and can easily locate in the future because I’ll need to refer to it with some frequency. I’d like to keep it in the Inbox and not move it to a separate folder. Is there a way to do this? I’m using IMAP.

That is exactly where you would use the flag.

Can you explain what you mean by the flag seems only to be temporary?

Problem fixed! Thanks for the reply.