We're aware that this is a request from users in Outlook. When using Outlook, you can select a subject of an e-mail, then edit it to be more fitting, making it easier to find by search/sort.

In GMail, there is not any way to edit a subject of a received e-mail - only when sending/forwarding/replying. Because the way GMail allows you to search and sort (by labels or other operatives), you may find it faster/easier/better to simply "search" for the messages based on a label you've applied.

See our section on searching based on specific keywords, characteristics, etc.