The ender dragon and wither spawn egg's are obtainable but not in the creative inventory it must be mistake Beacuse the iron golem and snow golem spawn eggs are there.
Comments 2
This is intentional:
Ender Dragon and Wither Spawn Eggs will only be available through commands to prevent accidental destruction of player builds
https://www.minecraft.net/en-us/article/minecraft-snapshot-22w44a
Do you middle click using pick block to pick ender dragon & wither spawn eggs, When you reply?