Ok, I think I see what you're saying -- use the category filter to show only those patches assigned to that category in a given bank. I think the answer is that it currently does not allow you to do this, there is only the category button at the top and once you save a patch (in any library) with that category assigned, it will group them all together (in other words they intend category to be like a search-across-all feature).
I can see it would be useful if category could be applied to current bank, but I guess they figure that within the scope of one bank its easy enough to scroll through? Also some folks might call with support questions of "why is my bank showing as empty! I lost all my patches dammit!" when really they forgot they have the filter set to "Organ" but they did not categorize patches as being organ patches... lol.
I know that sounds crazy to some but as a software developer myself, sometimes we have to take support costs into consideration and you have to design the user interface to have just enough flexibility to get the job done, but not enough rope for the user to hang themselves. Too much customization allows the user to paint themselves in a corner then it takes many expensive man hours to help rescue them
This is what I meant earlier by "individual workflow". What you want to accomplish (i.e. be able to get to your favorite patches for a given category quickly) can be done, just have to get a little creative in your workflow design. For example like I said, for me I group them by column rather than chronologically or some other order. For example if first two columns have empty slots, in means I can copy more bass patches there, etc.