The Only way I found to SEE the SDCard on my Windows 8.1 PC is to Open Fire Then you will see the picture you posted. When Side Loading in the List that drops down ALL I see is the Fire. Just No Way to get to the SDCard! There is now way to Transfer items OFF the Main HD on to the SDCard. That I have found.

When you Toggle those switches to the On position in Settings>Storage things you DL to the Fire are suppose to go there. But on my Fire 10 they Don't! I Forced the Apps on to the SDCard. That ALL that show on my card.
Purple Lady I tried what you posted all it did was mess up my Fire. Couldn't even Conect to WiFi ... had to Uninstall the ES App.