@asad009: Are you using the editor tool in the Gallery app > 3 lines in the bottom right > Videos > Select video > Tap the pencil symbol at the bottom of the screen? If so, what happens when you finish editing, and hit 'Save' at the top of the screen? Typically it should provide a flash notification to indicate the save location, and a notification should also be visible when you swipe from the top of the screen to the bottom.
@asad009: Is this the same for all videos you try to edit? Are they stored in your internal storage, or externally? If you tap on the resolution in the top left corner during the editing process and select High Efficiency Video, does this help? Try restarting your Z Fold 3, then head to Settings > Apps > Gallery > Force Stop > Storage > Clear Cache. Also, check the Galaxy Store > 3 lines in the top left > Updates, to see if there are any available updates for the Gallery app that might address the issue.
Hi Andrew, I'm having the same problem too. My photo editor was doing ok last week but last night I tried to edit/cut/trim a video but suddenly I couldn't save it. Tried following the instructions here but it's still the same. Can someone please help me?