How to change the current active partition slot?

How to change the current active partition slot? fastboot change slot But I want without fastboot command My usecase is the bootloader need to check the currect active slot and set the proper suffix How can I fastboot_ error_ failed to identify current slot Fastboot firmware, ZIP firmware is official from Xiaomi EU ROM, TWRP and Card slot microSDXC Internal 64GB 4GB RAM, 64GB 6GB RAM

fastboot getvar currentslot To enter fastbootd mode, bootloader writes boot-fastboot into the command field of the BCB message and leaves the recovery field of BCB unchanged (to enable