Find a naturally spawned bee nest.
In creative, break it when their are bees inside, and you should be able to pick it up again. Continue placing and breaking this bee nest. You should start to fill up your hotbar and inventory with bee nests.
Some bee nests will have stacked, and others not.

Reproduce

• Be in Creative
• Get a Bee Nest with NBT
• Break it for a bit
  Notice stacking issues occuring