In expand, you can use: routingStatus, presence, conversationSummary, outOfOffice, geolocation, station, authorization, lasttokenissued, authorization.unusedRoles, team, profileSkills, certifications, locations, groups, skills, languages, languagePreference, employerInfo, biography
These are the same values than the ones supported for GET /api/v2/users/{userId}
There is unfortunately no document at this stage describing the support fields.
There is an opened action to have it documented. But I don't know when this will happen.
Some of these fields are mentioned in former posts on this forum.
"id": id of the user (userId)
"email": email of the user
"name": name of the user
"routingSkills": skill the user has (this one uses the skill name)
"languages": language the user has (uses language name)
"manager.id": id of the manager (userId of the manager)
"divisionId": id of division the user belongs to
"groups.official.guid" and "groups.social.guid": id of groups the user is a member of
"location.location.value.guid": id of location
And on other fields from contact/user details:
"department"
"profileSkills"
"certifications"
"addresses"
"primaryContactInfo"