Congratulations on your tenacity and on solving the problem. A warm welcome to you, from New Zealand.
I was going to point you in the direction that you eventually used, with expert help from muungwana (using PCC and toggling to Expert mode to tick the User.) But, I wouldn't have been able to assist with the non showing of a partition.
When I first started to use this distro seriously, I found difficulty in getting access to data partitions too. It took a fair amount of head scratching before I found the same method here in the forums.
Now, sit back and enjoy the power of your FM version.