if i understand what you want, then i know of two ways
rclone lsf -R --files-only --include=*.jpg remote:folder1 > thedirs.txt
for /f %%u in (thedirs.txt) do rclone copy remote:folder1/%%u remote:folder2
you could do a rclone mount remote:
then use file manager to select all files in a flat view of folder1
use file manager to move those files to folder2