Everybody seems to have a different idea of what you mean by your question. I interpreted it to mean that you’ve got files on your USB stick that you don’t want to lose and you also want to be able to boot off of it.
If I’m right about what you’re asking, the short answer is “yes”. It’ll require some research to get all the pieces put together right. The specifics will probably depend what bootloader you put on the USB stick, what filesystem you have set up on the USB stick, whether the stick uses an MBR or GPT partition table, you’re booting via legacy BIOS boot or EFI, etc. But here’s a place to start: https://wiki.archlinux.org/title/Multiboot_USB_drive#Using_Syslinux_and_memdisk
Everybody seems to have a different idea of what you mean by your question. I interpreted it to mean that you’ve got files on your USB stick that you don’t want to lose and you also want to be able to boot off of it.
If I’m right about what you’re asking, the short answer is “yes”. It’ll require some research to get all the pieces put together right. The specifics will probably depend what bootloader you put on the USB stick, what filesystem you have set up on the USB stick, whether the stick uses an MBR or GPT partition table, you’re booting via legacy BIOS boot or EFI, etc. But here’s a place to start: https://wiki.archlinux.org/title/Multiboot_USB_drive#Using_Syslinux_and_memdisk