Thanks for the script!
But I can't get it working.
The workflow opens Firefox but keeps it minimized, and when I open Firefox it opens the startpage only?
I now have just the Run script action, I deleted the open Url action.
With this code
property _delay_after_launch : 3
on is_running(_name)
tell application "System Events" to return count of (processes whose name is _name)
end is_running
on run (argv)
set _url to first item of argv
set _running to is_running("Firefox")
log "_running=" & (_running as text)
if _running = 0 then
activate application "Firefox"
delay _delay_after_launch
end if
tell application "Firefox" to open https://www.blender.org/
end run