@mundodisco I don't have the knowledge to answer this question properly, but Recalbox is a LINUX-based system, so research on how to edit GRUB on Linux and try to do the same on Recalbox, the basic commands should work.
To change the GRUB image, I know that there is GRUB CUSTOMIZER, but I don't know if it is possible to install it on Recalbox, I never tried it, it may not be possible, because Recalbox abdicates many features to reduce the space used by the system.
See this link, it might help you:
https://unix.stackexchange.com/questions/422104/make-grub-boot-on-default-without-waiting
Note: When finished, please post the solution here, maybe your answer will help other people with the same problem.
