Using vegetable scraps are a good way to make vegetable broth. You are also correct that a pressure canner is the safe way to can meats, vegetables and soups.

Unfortunately, the National Center for Home Food Preservation doesn’t have specific canning recommendations and times for vegetable broth. You can freeze your scraps until you have enough saved up to make the vegetable broth. Instead of canning the broth, you can freeze it in freezer containers.

Here are directions for canning vegetable soup: https://nchfp.uga.edu/how/can_04/soups.html

Here are directions for canning meat broth: https://nchfp.uga.edu/how/can_05/stock_broth.html

I’m sorry there are not recommendations for canning vegetable broth. As you consider other recipes to can, you might want to look around at https://nchfp.uga.edu/