We haven’t built an ISO yet for this branch. But if you don’t mind waiting a day or two we may have a solution or workaround. Either an ISO as you suggest, or potentially just an updated bootloader file that you can drop onto the VFAT EFI System Partition of the USB disk (& again to the installed system)
On my own (older) XPS 13 it’s not possible to enroll a binary as trusted in the BIOS menu as noted above. It does have the option of appending a db entry, which is equivalent, but is a process even more fiddly to undergo.