Thanks for getting in touch!
Once you have selected a target you should be able to use the dropdown menu to select another target.
You can only select one target from the dropdown at a time though. So, if you want to include 10 targets you will need to open the dropdown 10 times and select each target to add it to the list.
If you’re needing to perform this regularly for a large number of targets then it may be worth reviewing the Target Roles assigned to your targets and deployment steps to see if they can be tightened or a new one added to decrease the number of servers being selected.