Mistakes are part of building. What matters is how fast you recover. SnapPages does not offer a keyboard undo the way a design app does, but it has Version Control built into the page editor, and that is your safety net.
Open the page you want to fix. Look for the Version Control panel in the sidebar. Every save the platform makes shows up there with a timestamp. You can preview any prior version before committing to it, which means you can check that the version you are about to restore is actually the one you want.
Once you confirm the right version, restore it. The page snaps back to that state and your current bad edit goes away. It is not glamorous, but it means you can experiment freely without fearing you will break something you cannot recover.
One habit worth building: before a big edit, save a manual version as a checkpoint. That gives you a labeled point to return to instead of scanning timestamps.