How to put Raise Skeleton back on your bars - Necromancer Diablo 4

Open the skill shortcut menu (default s key) Drag it in.
The button for the shortcut menu is also on the bottom of the talent screen.

For consoles, push L3 on the talent screen, then add from bottom

Here is the step by step PlayStation solution:
Press the Start button to open character inventory.
R1 twice over to Abilities.
L3 (Left Joystick click) for Skill Assignment.
Select Raise Skeleton by hitting X.
Assign Raise Skeleton to Triangle.