Minecraft – How to break through the bedrock ceiling in the nether

The 'Pick Block' key does not work to duplicate items on Bedrock edition in creative mode at the time of this writing (v1.16.201 on Windows 10).

However, duplication can still be done by duplicating a container.

1. Place a shulker box and load it up with items that you want to duplicate. This is nice for heavily enchanted items because it's a pain to place all those enchantments all over again for each item.
2. Break the shulker box and pick it up. Hovering over it will show a brief description of what's in it.
3. Now this same shulker box can be placed as many times as you'd like, it won't leave your inventory, effectively duplicating everything in it.
4. Note: Attempting to use the 'Pick Block' bound key on these placed shulkers will only pick an empty shulker box. You'll need to pick one up and continue from step 2 to continue duplicating the items within them.

In the world settings on the server menu before you join and find "Cheats" the first tick there is "Activate Cheats" make sure that is ticked on. When you are in game tap the pause button and click the icon next to your name. Make sure it is a crown and has "Operator" ticked.