Click on each unit or building you wish to make unmanned and give it a name inside the object property box (Example: unit001)
Then go to Edit->Scripts and make a new script inside the folder "plyrcivilian" with these settings
If
'true'
Actions if true
(Make a new action and go to Unit->Status->Make unmanned)
"Make unit 'unit???' unmanned"
Click on 'unit???' and change it to the name of the unit, it should be in the list.
Copy the new actions and click Edit on the copyed action, and change the name of the unit. Repeat this until all the units have been made unmanned in the script.
(the reason you copy and edit it, is because it's faster then going to "new" each time.)
Email me if you ever need help (edited signature November 6th, 2014)