Ventoy must be installed in a whole disk (USB drive or Local HDD/SSD disk).
So you can install Ventoy to the D: (Suppose C: is your Windows) and boot Ventoy from BIOS.
By default, Ventoy2Disk.exe will only list the device removable and in USB interface type. If you want you can run from cmd Ventoy2Disk.exe -U then all the devices will be in the list.
In this case you must take care about the list and make sure to select the right disk.
So you can install Ventoy to the D: (Suppose C: is your Windows) and boot Ventoy from BIOS.
By default, Ventoy2Disk.exe will only list the device removable and in USB interface type. If you want you can run from cmd Ventoy2Disk.exe -U then all the devices will be in the list.
In this case you must take care about the list and make sure to select the right disk.