After melding several 2 x materia equipments, I find the following aspects of the UI tiresome.

1) Have to scroll through half my items to locate the Materia
-> Like so many others have posted before me, separate tab please.
[Use Case 1]
I want to be able to see all my materia without clutter from other items.

[Use Case 2]
I want to be able to see all the materia I can currently attach to a selected item at the top (or bottom) of the list. (a.k.a. Improved sorting)

2) Unable to tell quickly why I can't meld a certain Materia until I click on it.
-> Materia that can be melded to the selected equipment should be "grayed out" differently from other types of "unable to meld", such as requirement not high enough.
-> Or perhaps give a different icon for each type, stacking them if necessary.
-> Or removed entirely from list if not usable for slot.

[Use Case 1]
I want to be able to quickly tell which materia I can use so that I can go buy the medium for it.

[Use Case 2]
I do not need to see the any of the materia that I cannot use for a selected item.

3) Unable to check quickly the melding chances of all the materia I am carrying - The repeated standing up and down makes it all the more annoying.
-> Chances to meld should be displayed in the materia list.
[Use Case]
I want to be able to know at a glance which materia I have the best chances to meld with.