Yes, it is possible. You'll want to use the find and replace function. Take existing text that's in all of your listings and add your line in there. For example, if your listings say something like:
Terms of service line one. Terms of service line two. The end.
and you want to add in a line between 1 and 2, you'll find and replace those lines with your new text in the middle like this:
Terms of service line one. NEW LINE HERE. Terms of service line two.
While you're making changes I suggest cutting down your terms of service by about 90%. Most buyers will not read all of that - it's a turn-off. Your descriptions should be concise and easily readable.
Your terms of service should include the bare minimum and not tell buyers they need to refer to photos for things your description may miss. Your description should include any relevant flaws, etc without a buyer having to magnify and examine each photo like it's part of a crime scene trying to figure out what the seller didn't disclose.
