This is where it's nice to have a client that edits raw messages. Such as mutt. Then you can edit Subject lines to have better search terms.
In my experience, most mail user agents allow editing the Subject header. Even Outlook Web Application that I have to use in work allows me to change the Subject line when a conversation thread has veered off-topic, e.g., “Server replacement [was: Windows 11 upgrades of client PCs in Accounts]“