Hello @akatsikad
When checking the issue history log for assignee changes, there are no details about the groups, which would require a calculated field.
That makes it impossible to know which groups a user belonged to when assigned to a ticket.
Therefore, you can’t calculate the transitions to/from group users, unfortunately.
The only way I can imagine is a Jira scripted field that returns integer 1 for each date when ticket was assigned to user in a different group, but I can’t find any examples to share for such scripted field.
Martins / eazyBI