You can merge multiple notes from the same notebook or different notebooks using the desktop version of Evernote. To start, select all the desired notes and click the Merge button in the right panel or right-click to merge them. The merged note will be named after the first selected note on Windows and the top note on macOS. If you want to undo the merge, restore your pre-merged notes from the Trash folder, delete the merged note, and then remove any remaining duplicates. Evernote also offers integration with over 1,000+ apps for further customization.