As the sd card uses a Linux partition, you can probably just install a Windows driver that lets you read and write on such a partition. I haven't tried recalbox yet, but for ext3 or ext4 drives I have used succesfully ext2fsd
Read this : https://www.howtogeek.com/112888/3-ways-to-access-your-linux-partitions-from-windows/
Or just download and install https://sourceforge.net/projects/ext2fsd/files/
Reboot your PC and insert your sd card.
Cheers.
Don't forget to eject your sd card from Windows when you have finished to copy your files.