every time i change something in the config entities become invisible

Doesn't happen on my end. Please specify all the mods you are running, Miencraft version and Forge version. If you are using a modpack, let me know what modpack.

Okay so this was frustrating me in my modpack and after I figured out either Catalogue or Configured was the cause I was even more confused and annoyed and basically spent too long testing and whittling down my modpack and basically it seems repeatable with just these mods:

(Forge 40.1.53 and Forge 40.1.54 - I thought .54's rendering hook changes or whatever may have been the cause, but no)
Alex's Mobs 1.18.6
Citadel 1.11.3
Catalogue 1.6.2
Configured 1.5.3

Process I did each time to test:
Load game (obviously)
Open Mod Menu
Close Mod Menu
Open Resource Pack Menu*
Close Resource Pack Menu*
(*no idea if these two are involved but I did it each time anyway)
Go to Singleplayer
Open a world

First and third person player model, entities, blocks in JEI (if installed), and breaking particles will all be invisible.
No idea why still, but at least I know which mods are the cause now.

So it's difficult to explain. Basically to render mobs from Alex Mobs, the world needs to be loaded. If you notice, the creative tab icon for Alex Mobs actually renders the mobs. Catalogue is using the tab icon to as an icon in the mod list, however since the world is not loaded it will cause an error. This error causes something internally to break rendering. The best fix is that Alex Mobs specifies an icon for Catalogue that doesn't need the world loaded to render.

Thanks for the help. I will take a look into the problem soon.

I've made a PR to alex mobs that fixes the issue. Expect a new release from their mod which resolves this issue.