More categories - Githubissues

Short Description

First step into making more categories within 1 category

Added a flexCategory

N/A

[ ] I have fully tested the proposed changes and promise that they will not break everything into chaos.
[ ] I have also tested the proposed changes in combination with base Slimefun and made sure nothing breaks/unexpected happens.
[ ] I followed the existing code standards and didn't mess up the formatting.
[ ] I did my best to add documentation to any public classes or methods I added which may not be obvious to maintainers.
[ ] I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values