A user asked if they could move folders from their IMAP account (which is near quota) to a pst. She didn't want to archive the messages because she wanted better control over which messages were moved.
Of course, you can move folders between data files! While you can just drag the folder to move it, it's usually easier to right click on the folder you want to move and choose Move Folder or use the Move > Folder button on the ribbon. This will quickly and easily move the folder to the selected data file. You can move selected messages to another data file by dragging or using the Move to folder command.