This is not possible on a client-side mod but it's a great idea for a new mod! I might make this if you give me permission
Update 1.11.6 (MC 1.11, 1.10.2, 1.10, 1.9.4, 1.8.9, 1.7.10):
+ Added automatic multi-world server support for waypoints.
All your waypoint files will be backed up to XaeroWaypoints/backup folder, incase something doesn't work as intended.
+ Added Minecraft Realms support for waypoints.
* Fixed the minimap crashing sometimes when switching between worlds.
* Fixed issues caused by Minecraft automatically replacing dots with underscores in world names.
* Fixed not being able to use ":" in waypoint set names.
Yes, please. It's just an idea, if you can make it a reality that would be sweet. Permission granted, please let me know when it's made,so i can use it!