This app is used in development to design and create system content-types. Examples are
- @All - the type used to define a field
- @string-dropdown - the type used to configure a drop-down field
- @string-dropdown-query (2sxc 9.10/9.12)
- @entity-query (2sxc 9.10/9.12)
This app is very difficult to install, because it must circumvent certain automations on the EAV. So you can't just install in on any EAV / 2sxc.
I'll write some instructions some day, but ATM just be aware of the fact that it's not easy, but that's by design.