How do I set up the default location of downloads to external SD on my elecost tablet?

Solution
You probably can't, cheaper devices and those on older Android versions don't have the option to format SD as internal storage. You should be able to move files there manually when you download them with File Manager and set the Photo and Video apps to use the card for saving to.
You probably can't, cheaper devices and those on older Android versions don't have the option to format SD as internal storage. You should be able to move files there manually when you download them with File Manager and set the Photo and Video apps to use the card for saving to.
 
Solution