NESinjector will inject your roms by renaming them, but also convert your covers (.jpg) format and sizes so that they are recognized by the emulator and all that in one click.
Indeed, it will rename your roms, copy them directly into the folder clover / user / rom / ..., then convert your covers in .jpg format to .png and resize them to specific sizes, then move them directly into folders clover / user / boxart / ... and clover / user / thumbnail / ...
Moreover, it will create the famous data.json file (which allows the recognition of your new injected roms) and will automatically move it to the clover / user / ... folder.
Finally, it will also create a saveroms folder to save your already injected roms and automatically copy them into a roms folder (which you will have to create) with each new injection of new roms.
NESinjector will create a new data.json file and overwrite the one already present which will make you lose the roms already present in the emulator, to keep these roms, copy them in the folder roms before injecting your own roms.
HOW TO USE:
Uncompress the .rar in a folder containing the clover folder of Nes Classic Emulator (see photo below).
Create a folder roms and copy / paste the roms you want to inject in (and also the roms already present in the emulator if you want to keep them
Place your covers in .jpg format next to NESinjector.exe (see photo below)
WARNING: rename your covers with the same name as your roms
for example: my rom is named Dragon Ball.nes, rename your .jpg in DragonBall.jpg by removing the spaces or -, *.
Click on NESinjector.exe and wait a few seconds, if everything went well a saveroms folder will be created with a backup of your roms (do not delete it).
Last very important thing (the bug in question) open the file data.json just created present in clover / user / ... with a text editor (notepad or other) and delete the last comma (in red in the quote below) at the very bottom of the code.