Please either add a way in the configs to change the render distance or greatly reduce the distance at which these are visible. You can see a Voidblossom boss bar from hundreds of blocks away.

Actually, this is just how the boss bar works in Minecraft. Vertically it goes basically infinity and horizontally there is a limit. You can even test it with the wither.

Wich version are you playing?

I assume it's happening on all versions but specifically 1.20.1