"Last activity" not entirely what it looks

[Joost Sanders]

The "Last activity" field seems to only be updated on either a new customer reply or a staff reply.
If that is correct, it should be called "Last reply".

Last activity, to my opinion, should also be the date/time that staff did anything that changed the ticket. So, yes, posting a reply should update the last activity field. But, changing the status should also do that! Or releasing to another staff member.

We have for one department a workflow that is (simplified) like this:
- New (on arrival)
- Reviewed (with post reply to customer)
- Open (assigned to staff member to resolve, no reply to customer)
- Fixed (assigned to senior developer, no reply to customer)
- Verified internally (no reply to customer)
- Released to acceptance (reply to customer, waiting for approval)
- Verified customer (assigned to senior developer, no reply to customer)
- Released to production (reply to customer)
- Closed

And some more statusses for alternative paths but that is not relevant for now.

What we need is that the "Last activity" field, is updated on each of these status changes / actions. Or another field that is sortable in our views.

Any idea how we could manage?