You don’t need to put F: into the path field, this will be set in lv_conf.h instead. In the path field you only need to set the path where you want te asset files to be looked for on the target system. (In the exported code ‘assets’ will be under ‘drive/’ but if you use it in other path (given in the ‘Root path’ field) on the target platform, you’ll need to copy the assets folder with its content there.