When a batch of notes belongs somewhere else, should become one note, or should go altogether, selecting them saves doing it one note at a time. Once several notes are selected, moving, merging and deleting act on all of them in one go, and moving and deleting never touch a note's modified date.
On desktop
The list works the way the Apple Notes list does on a Mac. Hold Cmd on Mac or Ctrl on Windows and Linux and click notes to add each one to the selection, or hold Shift and click to take every note between the last one you clicked and this one. With the list focused, Cmd A on Mac and Ctrl A on Windows and Linux selects the whole list. Every selected note is highlighted and the editor shows how many are selected. Right click any selected note for what can be done with all of them. A plain click on any note, or Escape, goes back to a single note.
On mobile
Open a folder and choose Select Notes from the menu in the header. A checkbox appears beside every note, and tapping a note checks it instead of opening it. The header menu offers Select All and Deselect All, the count shows under the folder name, and the bar at the bottom of the screen holds Move and Delete. Tap the check button in the header to leave without doing anything.
Moving them
On desktop, right click any selected note and choose Move to Folder, which opens the whole folder tree, subfolders included, or drag the selection onto a folder in the sidebar. On mobile, tap Move in the bar and pick a destination from the sheet. Every selected note moves at once, and pinned notes, tags and note links come along untouched. The move article covers moving one note.
Merging them
Merge Notes in the right click menu on desktop, or Merge in the bar on mobile, makes one new note out of the selection. Before anything happens you see the notes in the order they will follow one another, which is the order they have in the list, and can still cancel. The new note starts with the first note, so that note's first line becomes its title, and a rule separates each note from the next. Everything comes along: formatting, images, recordings, drawings, flashcards, quizzes, mind maps and slide decks. The originals move to Recently Deleted, from where any of them can still be brought back. Handwriting notes cannot be merged, since their pages are ink rather than text.
Deleting them
Delete Notes in the right click menu on desktop, or Delete in the bar on mobile, sends the selected notes to Recently Deleted, from where any of them can be brought back. On desktop the delete shortcut, Cmd Backspace on Mac and Delete on Windows and Linux, does the same. Inside Recently Deleted the same action deletes the selected notes permanently, after asking once for the whole batch.