The Move to Bottom button is available on the ClipHistory toolbar. Click it to move the selected clips to the bottom of the ClipHistory.
The Move to Bottom command is also available in the Clip menu. It is enabled when the ClipHistory tab or an AceText Collection tab is active. In a collection, it moves the selected clips and folders to the bottom of the collection. If the collection is sorted, then it moves the selected clips and folders out of their parent folders into the root of the collection. They are then sorted between the other clips and folders in the root of the collection.
In the Operation Preferences there are options for automatically moving clips to the top of the ClipHistory when they are copied again by another application or when AceText sends them to another application.
See Manage and Arrange Text to learn how to use AceText.