Steps to Reproduce:
Make sure “Hide HUD” is turned off
Get any mob effect in any world
Observe the effect icon
Leave the world
Apply or remove any resource pack
Re-enter the same world
Observed Results:
The effect icons stops being displayed entirely, and only shows up again after you close and reopen the game.
Expected Results:
The effect icons show on the side of the screen regardless of whether you changed resource packs in that session or not.
Notes: Pressing the keybind still opens the full effect screen as usual. I have not yet tested on mobile, where the lack of icon could also affect the user’s ability to open the effect screen.