Currently this facility of Multiple User Select field is available for Communication Table only. It does not work for other tables because the User multi select writes into a field of data type ‘Int’ and as an ‘Int’ field it could not store multiple values in same field and needs a link table to store this information in the link table. In communication the user multiselects are stored in the comm_link table.
We can do a trick here to get round the need to put a User Multi Select into a table:
[1] Add a Dummy Translation with Caption_Code = MultiUserSelect, Caption Familytype = Choices, Capt_Family = Users, Capt_code =1
[2] Refresh Meta Data or Reset IIS
[3] Create a multiselect field (not a user multiselect but a normal
multiselect) and select the Lookup family here as “Users”;
[4] Add the field to the target entities Screen;
Try selecting More then 1 User.
Note: As per the communication record we could not able to see the record against each User selected while creating record. This is possible with communication table because communication has Link table for handling this process. This Trick will create a MultiSelect User field only.