ability to change your friends nickname

you guys should add an option where you can change your friends nicknames (that only you can view) so you don't forget who they are and you can identify them easier. this is because there are times my friends change their usernames and I tend to forget who they are and so I have to look back at direct messages or ask them who they are to be able to remember. i know there is a note option where you are able to write stuff under peoples profiles but sometimes the note ends up disappearing after a while and its really annoying. also, having an option to be able to change your friends names would also be easier than the note option because with the note option you have to click on their profile whereas if you had the ability to change your friends nickname you would be able to notice it immediately. please take this under consideration, thank you.