The most recent version of this documentation can be found at https://docs.dyalog.com/20.0/.
The )PROPS system command lists the Properties of the object associated with the current space.
For example:
⎕CS 'BB' ⎕WC 'BrowseBox' )PROPS BrowseFor Caption ChildList Data Event EventList HasEdit KeepOnClose MethodList PropList StartIn Target Translate Type
)PROPS produces no output when executed in a pure (non GUI) namespace, for example:
⎕CS 'X' ⎕NS '' )PROPS