Disk Genius can also be used to access the ext4 partition on the SD card.
Free version wont let you write to SD card though.
But,you dont even have to use ext4 file format.
The Batocera wiki covers this.
On my RGB10 Max for eg I use ntfs.
Procedure is same for A13.
Flash Batocera to the card as normal,let it boot then after first boot,shut it down then put the sd card in your PC and format the share partition. You can format it to ntfs or exfat for eg
If you are using windows 10 on your PC it should detect two partitions but your PC may already ask you to format it when you inserted it as it cant read the share partition thats in ext4.
After you formatted it to ntfs or exfat put it back in the device,power on. Batocera will then create the folder structure again this time on the newly formatted ntfs partition. (Note doing this will ofcourse delete all data currently on the partition so if you already have files on there you want to keep,back them up first).
Then you can simply transfer files over to the share partition using windows as normal.
No need for Paragon or Disk Genius
Ofcourse Batocera uses ext4 for good reasons,so read the info in the wiki link anyway as to why.
edit: As for scraping on it.
Do what I did for the PS7000.
Download and use scraper for PC. Set up your rom folders on PC,scrape whatever images/video snaps you want there then transfer everything over when youre done.
The beauty about doing it on PC is you have some more scraping image options,diff image types and you can even resize the images before download,since you would be using them on smaller screen you can set them smaller,so saving you storage space,sadly you cant resize videos before download,just images.