Currently, with Extra Services Addon, you add extra services in each service. In my case, I have the exact same 6 extra services for dozens of services. So this means I have add these individually, again and again, for each service. And, if my price changes, I have to go back through every single service to update each price individually.
It would be very nice to have an option -- or another addon plugin -- to make the extra service "global" so you can easily edit it once and it updates all of them. Ideally, it would be managed in its own section vs. in the individual services with possibly a checkbox system to assign it to applicable services.