I don't think there is but I 110% agree. It's annoying, time consuming and pointless that it does not mark them all as resolved. Seems like a bug to me but it still has not been fixed in 2 major version updates.
I'm kinda new to this so "right" or wrong here's what worked for me...
My WHD version is 12.0.0 - Build #188.8.131.526 but I think the process should be the same for a relatively recent version (don't quote me on that though)
- edit the ticket you want to mark as parent or master and change the "Ticket Type" to "Problem"
- if you've already opened a few tickets before discovering the trend, go back to them and change the "Ticket Type" to "Incident"
- now click on the "Problems" tab on the right of the main ticket to open some additional fields.
- under "Problem Search" I entered my master/parent ticket in the No. field and clicked "Search"
- click "Link" under Action. Your child ticket is now linked with the master/parent (a new Linked Problem field will show in your main ticket details area.
- from there I was able to go back to my master/parent ticket, update it with some notes, mark it as closed and the linked child tickets automatically updated and closed. No extra hunting for me.