Can use any tool able to query enqueues held by users. For example, ENQ command available from TSO ISRDDN utility. Once in the ENQ panel, query for enqueues with:
MAJOR NAME=ENDEVOR (to identify endevor users) or EDIT-ELM (to locate Quickedit users)
MINOR NAME= literal 'IS ACTIVE IN SESSION n'
Each and every TSO user holding one of the above enqueues is using the dialogs and has potentially allocated and open the endevor datasets.