I added the ability to split and merge documents, as well as select multiple documents in the File Drawer. The features are available from appropriate context menus.
To merge, select two or more documents in the File Drawer, right click on one of them, and select Merge Documents. The documents will be merged up into the first document. The other documents will be put into the trash.
To split, put the cursor where you want to split, right click and select split. If you select some text, you have the option of turning that text into the title of the new document (the text will be removed from the actual document).