This pack adds trial mobs, raiders, skeleton traps, withers and ender dragons to the locator bar. This makes prolonged fights less tedious and can especially be useful during raids if the wave spawns inside a cave.

It also gives trial mobs and skeleton horsemen bossbars, one per spawner and trap respectively. It can hold a maximum of 30 trial and 30 skeleton trap bossbars at a time. Any naturally generating trial spawners function perfectly, and so do any trial spawners that were customised using spawn eggs, they even have custom colours like other trial mobs.*

The pack should work immediately upon applying. If trial mobs were already present before enabling the datapack, it is possible they don't appear on the locator bar, which just means they were too far away from the spawner to locate it. However, the next time that spawner spawns a mob, it should be marked and all future mobs spawned by it will appear on the locator bar. Bossbars should then also start functioning if they weren't already.

Illusioners in raids are also supported, but if they turn invisible their position on the locator bar will be hidden (like when players have invisibility).

As far as permanent changes to your world go, this datapack should only affect the following entities (no blocks or items):
 - All loaded persistent mobs will be checked to see if there are spawners near them, and once they have been checked they will be given the tag "checked.for.spawner" to prevent unnecessary double checking. These tags have no effect on the entity outside of telling the pack not to check them anymore.
 - Trial mobs, raiders and skeleton horsemen have a "maintain.waypoint" tag. This tag has no effect on the entity outside of telling the pack not reset its waypoint_transmit_range attribute.
 - All skeleton horsemen also have a "marked.horseman" tag, and if they wander out of range they'll also get the "left.fight" tag. These tags also don't affect the entity, they just help the datapack keep track of them.
 - Any mobs that have been put on the locator bar while the pack is enabled will continue to transmit their location even after the pack is disabled unless you manually reset their waypoint_transmit_range attribute.
 - To be able to read the data of the trial spawners and skeleton horsemen, invisible markers are placed in their locations. These are used to store the positions of the spawners and to position the bossbars, and will be removed automatically if their spawner or skeleton trap gets destroyed. However, they will remain present after removing the datapack. If need be you can run the following commands to delete them:
/kill @e[type=marker,tag=trial.spawner]
/kill @e[type=marker,tag=skeleton.trap]

This is my first datapack so if you have any ideas for efficiency, bugs to report, or other suggestions, any feedback is greatly appreciated!

Ideas I'm considering:
 - A resource pack to customise waypoint icons, including a custom icon for raid captains and mobs in ominous trials.
 - Adding zombie sieges to the locator bar and giving them a bossbar. I am actively working on this but it is complicated due to zombie siege zombies being indistinguishable from regular zombies.
 - The ability to toggle whether bossbars show for trial spawners and skeleton traps.
Let me know if you agree with these!

*It is worth noting that when using a datapack that customises trial spawners, the bossbars will likely not display accurate values, as I have not yet found a way to read the configuration files. If you have any ideas for how to do this, please let me know.