Hello wehrmacher, can I ask if it is an NTFS or RAW partition? The disk management utility only works with these file structures.
Also, you could try changing the volume ( ie the disk, not the partition) to a Dynamic Volume and see if that helps.
Otherwise, yes, you may be running into a limitation of the utility, and will have to try one of the 3rd party ones. I have only used one before, can't remember which but I think it was something Wizard...