The short answer I don't know.
On my system the device shows twice in Folders as Samsung Galaxy, almost as other drives or volumes. I guess this is because I have sync’d photos from the phone which were in a folder on the SD card but I have also created a new folder in the LR mobile app, set to auto import. So each time I take a new pic using the phone it automatically gets sync’d to my desktop computer. To be honest I haven’t messed with the lrdata files as I take very few pics with the phone. I suppose they work via the Creative Cloud interface. But what I have found out is you can delete those images taken with the phone camera to free up space on the phone and the original synchronized jpegs uploaded to the desktop remain in place.
Well I've found one way, for Windows. Not sure how to do it on a Mac.
If you right click on the My Pictures folder and select Properties you can change the Location of that folder. I created another My Pictures folder on my E drive and selected that as the Default Location. Now everything synced from my phone's LR to my computer LR is placed in the E:\My Pictures folder.
I also notice you can't change the Default location in the regular Import dialog window. It always seems to default to the My Pictures folder.
Thanks for the response 99jon.
I have another thread open with another LR mobile question which I think I've figured out also. I won't know until I get home from work.