Hi Svante,
Once you draft your reply and hit the button "Send and set as closed" the system analyzes that the ticket has been closed and no further activity needs to be done on the ticket. The ideal way to perform actions here is that, we'll have to update the properties of the ticket first and then send the reply by hitting the button "Send and set as closed".
You can either just send the reply and then update all the properties or update all the properties at one go and send the reply and close the tickets. This has been the default behaviour in Freshdesk.
The focus assist on the other hand does the following process- On closing a ticket, it quickly moves to the next available ticket in your queue and not to the list of tickets as this increases agent's productivity.
Hope this clarifies.
Cheers!