I used to use a partition tool that could be burned onto a a disc which could then be booted from and the tool could recognise like, 20 different file systems and resize partitions etc. I think it used the same GUI partition tool as openSUSE but I can’t remember the name. Something-parted maybe?
You know, I think it was Gparted. GParted – LiveCD
There is also “parted magic”.
PartedMagic - Main - Parted Magic
IMHO both are good.