I have posted the solution elsewhere. This is the solution. Connect Kindle to USB. Run Calibre and the "device" appears on top line of Calibre. Click on arrow to right of DEVICE and click on "configure this device". Read down to where it lists the folders that Calibre copies the ebooks to. You can delete documents, leaving books, kindle. Books is now the first folder - calibre will now ALWAYS ALWAYS ALWAYS send ebooks to the BOOKS folder.
Note: You may also create a rule below that on the same page. Tell mobi docs to always copy to the BOOKS folder. This takes precedence over the "documents, books, kindle" folders.
Easy, Eh
