is there a way to access the stock wfa maps in the editor.
You need to unpack then from their archive file by running this command in command prompt from the CoH2 directory. I'm not sure how much you know about command prompt so I'll explain what I can.
1. Open command prompt in windows
2. Go to the directory you installed company of heroes at. (By default command prompt is "c:\users\username" ). So you'll probably want to type "cd C:\Steam\steamapps\common\company of heroes 2" depending where you installed the game.
3. put the following command into command prompt "Archive.exe -a CoH2\Archives\MPXP1Scenarios.sga -e CoH2\Data"
The maps will extract to that folder and you can just go to worldbuilder and open them now.