Hi @Krotosz6 , i have the exact same problem, the multitool doesn't detect internal memory (i guess you mean the emmc ?), i tried your way without succeess, would you mind write a step by step instruction ?
i can run armbian from sdcard but still the emmc isn't detected, i was assuming my emmc is dead, but reading your post gives me a new hope 🤣
i have different box, its h96max rk3318 with black pcb but the short pin looks similar, here's the pic :
(the green line is the short pin i usually used, yellow line is your short pin from what i understand)