Entity list is rather overwhelming

I'd suggest to list the entities in a tree list (roots would be the entity kind) and sort entities of the same type via distance to the camera or from left to right from the perspective of the camera. This would make it easier to match the list entry to the actual entity in the preview.
Another feature for the list could be an indicator, that the entity is currently not visible in the scene (because it gets covered by a non-transparent wall). I assume it should be possible to get this information by ray casting from the camera to the entity (use the scale as radius for a perimeter or something?). This would help to know which entities the user doesn't have to update to look good in the scene :)

Additionally, the selected entity could be highlighted in the preview using a red border, if possible, or a red dot/arrow indicator at the center of the entity.

And finally, I'd need a button to remove all entities of the same type (or even better, disable loading of selected types at all when reloading chunks).

Roundup of my suggestions:
- [ ] tree list instead of list
- [ ] sort entities by location relative to the camera
- [ ] indicate hidden entities -> don't have to add them to the bvh tree
- [ ] highlight entities in preview
- [ ] #465 -> select entities via clicking in preview window
- [ ] selective entity loading (allow/block list while chunk loading)