The Move Clips button is available on the collection toolbar, except when the Clipboard tab is active.
When you click the Move Clips button, a popup menu will appear below it. When you press Ctrl+M on the keyboard, the same menu appears to the right of the list of clips. The menu lists all AceText collections that you have opened, except the active collection. Select one of them from the menu to move all selected clips and folders into that collection.
If the selected clips and folders are inside one or more folders, the same folder structure will be created in the collection you are moving the items into. If the folder structure already exists in the target collection, the items will be placed into the existing folders.
See Manage and Arrange Text to learn how to use AceText.