I have tried on survival and creative to try and get multiple protection enchantments. I have seen that this is a new feature and wanted to check it out. Unfortunately, to my disappointment, the feature does not work. I tried combining at an anvil and tried enchanting at an enchantment table but it does not work.
MC-158905
Can not stack protection enchantments
Resolved
Duplicate
0
Chad Murphy
(Unassigned)
Unconfirmed
Loot tables
1.14.4
Retrieved
Thank you for your report!
We're actually already tracking this issue in MC-154025, so I resolved and linked this ticket as a duplicate.
However, that ticket has already been resolved. Depending on the resolution, that can mean that it either will be fixed in the next version, or that it is not considered a bug and won't be fixed.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.