All in the title:
How to keep particles and damage hits number but hide the top-left HUD ?

I would really want to only keep particles and the number of damage on hits,

Thank you so much,

Lunar

In the Config, You can disable the HUD elements as following.

"showEntity": false,
"showBar": false,
"showSkin": false

And then set inWorld mode to ALWAYS. (This is the feature where every mob has a bar above them) If you don't wanna have the bar and only the damage particles and numbers, just set the distance to 0.0:

"inWorld": {
"mode": "ALWAYS",
"distance": 0.0,
"onlyWhenLookingAt": false,
"onlyWhenHurt": false

That made the trick for me.