I have Fedora Xfce 37 installation .iso on a ventoy thumb drive. I want to install it on my M.2 drive in partition 6, which is currently formatted ext4. I get just so far: after I've selected custom install and set to reformat, it really wants to create a new partition (number 22) and won't let me select partition 6 for the purpose. It does not help for me to use gparted to clear the partition -- in this case I cannot get the installer to stop trying to claim the whole drive and presumably erase the partitions I already have. I've also tried to let it set up partitions automatically and then modify: I still can't get it to use the partition 6 space for root.
Since 256 GB is clearly enough space, is there some way to get Fedora to sandwich itself into this space? The only previous question that seemed close was 6 years old with no votes and just one answer (that did not work for me - I did not get the same response from the installer.)