I wanted to give Plasma another go, so I installed the plasma spin on separate partition and now the new installation overwrote the EFI entry for my old gnome installation and I’m unable to boot back to the previous install. How can I get it back and recreate the EFI entry and name it something else than ‘fedora’ so that they won’t clash again?
I am not sure you can easily.
Probably you can boot to the live usb then mount the drive partitions of the previous workstation. Once there you may try to copy everything in the /boot/efi/EFI/fedora to a new directory you can name as you choose. (/boot/efi/EFI/fedora2 or similar) The new directory would become the efi directory for one of the 2 systems.
You can easily recover the prior booting system by doing the above then doing a chroot to the mounted system and running
grub2-mkconfig -o /etc/grub2-efi.cfg
There are a lot of posts on the Linux Questions forum about similar issues with the various flavors of ubuntu and all using the ubuntu name for efi boot.
The only significant difference between the standard and plasma spins is the DE so the much easier way would have been to simply install the plasma DE on your existing workstation. You could then have selected plasma or gnome from the gear at the lower right of the login screen prior to entering your password.