idea: personal subject-lines for emails.
#gmail. Some emails you just read the once and never come back to them. Other emails contain information you'll want to reference in the future, which means you'll need to be able to find them again down the line.
There's lots of things that help in your search for an email - like knowing roughly when it was sent, so you can scroll down to that point in your inbox, or knowing terms mentioned in its body, so you can search on them. Sometimes you scan the subject-lines of the emails in your inbox or search results.
But sometimes those subject-lines are aren't very informative.
Some are just too generic (like "hi"). Or they may just not be specific enough for what you're looking for.
At the times when you know you'll want to find an email again later on, and it's obvious to you that the current subject-line isn't going to be that helpful, it'd be handy if you could stick a 'custom subject-line' over the top of the existing one.
After you'd added this custom subject-line in your inbox, that's the subject-line you'd see for that email, but it'd be clearly distinguished to show that it wasn't the original subject-line, and there'd be a way to find out what that original subject-line was.
As with any possible feature addition, the question is whether its benefits exceed its costs. This feature would be handy in some situations, but is the additional overhead in the UI and effort to come up with and type the new subject-lines worth it, for example? I doubt you could really tell if it's worth it for a feature like this unless you tried it out. You might get some idea from thinking through, in a lot of detail, scenarios of what the UI and usage-experience would be like if it existed.
