Non-destructive vs destructive external editing
Non-destructive is the default: Edit in Photoshop, Lightroom or any editor you have added hands the editor a copy, your project switches to the copy and the original file is never changed. Choose Destructive under Image Editors in Settings if you want saves to overwrite the original where it lives.
Starts at 3:46 in the 1.3.9 release videoWatch on YouTube
More in Settings & preferences
See all 13Low resolution and DPI warnings59:03Keep the existing template when you remove an image52:59Keep the opposite page when removing an image53:37Match aspect ratios or preserve order (retired in 1.3.5)54:08Image placement mode (retired in 1.3.5)52:14Reset zoom and pan on template change54:42Turn template hover previews off59:35Turn the edge drop overlays off1:00:02Stop blank spreads appearing at the end1:00:25Jump to a spread after dropping photos on it1:00:37Automatic page numbersGuideThe Return Folder for Lightroom exports5:25