Can you retrieve an enemy's attack IDs with plotscripting?

Yes, you can.

All enemy data that you enter in the Edit Enemy Stats menu can be accessed with commands plot:read enemy data and plot:write enemy data. get/set enemy name/stat/appearence are wrappers around these commands.

These commands access raw enemy data directly. Only some items of enemy data have constants defined in plotscr.hsd (such as enemy:gold). For the rest, see DT1.

For example, to read the first normal attack from the enemy with ID enemy, you would use

normal attack 1 := read enemy data (enemy, 92) -- 1