If you're trying to boot from an external SSD with Win 11 on it that's connected to PC via USB (USB-c?), I doubt that's going to work. It likely exceeds the size limit, has the wrong format, etc. As a test, create a bootable  USB stick using Rufus (free) with FAT32 format, or use the Microsoft Media Creation Tool for Win 11 and see if either of those boots this PC. You can use a USB 2-GB stick with Rufus or an 8-GB stick with the Media Creation Tool.
When I need boot from USB drive on my XPS 8950 desktop, I surprisingly find out there is no USB BOOT item in the Boot sequence of BIOS (press F12 on startup) and could not setup that in BOOT tab of setup screen (F2) neither. the BIOS version is 1.13.0 (newest version on 2023/4/12) Anyone knows what's going on here and how to solve this issue? Thank you guys.
XPS 8950, boot from a USB drive?