This mod allows for visualizing what chunks are forceloaded in your world. This mod works through the vanilla /forceload query command, so it does not require any server-side functionality to work, although if others are running forceload-related commands, you may become desynced and have to run /forceload query or /forceloadtools update to get back in sync.
Enable/disable the overlay with the /forceloadtools [enable/disable] commands.
Update the list of chunks with /forceloadtools update. The list will also be updated every time the mod sees that a /forceload command has been run.