Thanks for your help Fredrik71. When running the script I now get an error message “Can’t set bounds of window to {0, 0, 1250, 930}”. This occurs regardless of the app from which the workflow is activated. This is a copy of the new script:
on run {input, parameters}
tell application "System Events" to set currentApplication to name of first application process whose frontmost is true
tell application currentApplication
tell window
set bounds to {0, 0, 1250, 930}
end tell
end tell
return input
property theBounds : {{0, 0}, {1250, 930}}
tell application "System Events" to tell window 1 of (process 1 whose it is frontmost) to ¬
set {position, size} to theBounds