As of November 20, 2020, we made an important to change to our Content Editor that will simplify and save you time as you develop content pieces for "All Networks" and for each network individually.
You will notice that the networks are now in a subfolder system.
All Networks will appear at the top, with the others follow below.
When you're working in the "All Networks" tab - all your activity will cascade down to all subfolders/networks below. Once you make a change to an individual network, those changes will only apply to that network, and therefore, you will not be able to make changes across "All Networks" anymore.