Opening external apps one after the other

I have created a button to an external application called EditPad Pro and when I multiple select text files they will all open in separate tabs within one instance of EditPad Pro. However after I installed Opus all text files are now opened one after the other after closing the current instance of EditPad Pro with only one text file opened in a single tab. This is very annoying since I used this feature a lot. Is there a way to set this right again?

Edit the button and put "@async " at the start of the line (not including the quotes).