I want it to act exactly as the built-in QB save button at the top right, but I want to add it to the bottom of the form page. I've tried a couple different formula URL ideas from the community, but none seem to work correctly.
Actually, I think I just figured it out so I thought I'd share. I was trying to accomplish this with a formula URL field for too long. I decided to try a formula text field. Here's what I ended up with:
"<img onclick='DoSaveAdd()' src='your web link for image'>"
This finally did exactly what I wanted, without any QB pop-up to save. It also returns me to the parent record, where I clicked the Add button.