Skill slots (or Ability slots, as the game calls them) are very important in Diablo 4. Each slot corresponds to a button or key and can be assigned an ability. However, there are a lot of skills and abilities in Diablo 4 and it can sometimes feel like you don’t have enough skill slots, especially early in the game.
Get 5th Skill Slot – General Helpful Tip for PC Players – Diablo IV
Luckily, there are ways to unlock more, but only in the early stages of leveling up. If you're expecting a large hotbar with tons of ability slots, you're probably out of luck.
At the start of the game, you only have one skill slot unlocked. You don’t have any abilities unlocked at the start, so your one skill slot is assigned to your basic attack. However, at level two, you gain your first skill point, which you can spend on an ability, and that ability is automatically assigned to your one skill slot.
At level three, you get another skill point, but no skill slot. So if you unlock a second ability at level three, you don’t have a slot to assign it to. I didn’t have a problem with this when I played as a Barbarian, but I noticed it right away when I played as a Rogue. I wanted to be able to use both melee and ranged attacks, but I couldn’t. Not yet.
