Now we have Total spent time on the issue list made via #11253. It works fine for normal issues, but not for parent tickets, it would be great to have same feature for overall spent time.

When you make a custom query that includes "parent tickets" and in your query option "Totals" you select to display "spent time" you get 0 above the query.

This is because the query only does a sum of the spent time of the "parent tickets" which have actually 0.

However from a user perspective the total spent time should be the grand total of overall spent time for each time.

see attached screenshot as a real an example.