leafpad note can't save to usb drive, even thou it is mounted as seen on nautilus

ubuntu 18.04lts

leafpad note can't save to usb drive (usb drive is not visible in the "save dialog box"
even thou the usb drive is mounted as seen on nautilus
when i used libre writer to save to usb drive, it is ok (usb drive is visible).

any idea why ? is there something to do with the way the software programmed or is there some sort of permission or right i have not done.

thx
andrew