Like every other Monster Hunter game, there is no health bar for enemies in MHW.
Enemy Health Bar
Monster Hunter Wilds is not an exception to other Monster Hunter games having no enemy health bars.
Your only option on knowing where you are at while fighting a monster is listening to your companions and waiting for the indicators to tell you when the monster is tired.
- A tired monster is very low at health.
Mods
"Heath Bars" in NexusMods [https://www.nexusmods.com/monsterhunterwilds/mods/16] is the only working mod you can use to have health bars for enemies in MHW.
1. Download and Install REFramework Nightly. (MHWILDS.zip)
2. Download Health Bars Mod.
3. Extract the mod from the archive and place it in /MonsterHunterWildsBetatest/ root folder. (place the whole reframework folder in game's root)