How to use Ventoy to boot os from external HDD

[xomox]

I have huawei matebook it won't allow to boot from external hdd only from pendrive. How to use Ventoy to boot computer from external HDD? (I have there Ubuntu installed but I can't boot it). I would like to boot from pendrive with Ventoy and the from it initiate boot process from external hdd with ubuntu on it.

[longpanda]

There are two ways to do so.
1. Use F4 local boot ---> boot 1st/2nd/3rd/ local disk
2. Write a customized ventoy_grub.cfg and use F6 to load it