In this view an organization’s administrator defines, which DSLs are available for modeling. If nothing is selected, all DSLs are going to be used. Unassigning a DSL that was previously assigned doesn’t delete any data. Only definitions of the assigned DSLs are going to be used in searches and in the element wizard.
Check the documentation for DSL management if you want to learn more about DSLs.
This is a screenshot of the active DSLs view: