Global XP Mod 1.13.2/1.12.2 is pretty straight forward. It adds an XP Block which allows for near infinite storage of experience which any players can access. (A fast way to store XP and share it with your friends.)
In the Creative Menu, that block can be found under the ?Miscellaneous ? tab.
To view how many XP is stored in the block, just look at it and a nametag-like text will pop up above the block showing an approximation of how many levels are stored and the exact value of XP stored in brackets (toggleable).