I don't see much benefit in being able to see ships and building simultaneously in the same list. That would make the "category" column obsolete.
The rightmost column isn't intended to be category. Rather, it's "short description", similar to what appears on the tech screen to describe a tech's or building's function in one line / five words or less. I just don't have / haven't written any such descriptions for any buildings or ships, so used "building" or "ship" as filler.
I question the usefulness of seeing un-researched items in the list, but i realize some people have requested it. I'd rather see such things listed in our "Orion-opedia" help/info system.
Having un-researched items selectable on the list is useful because it allows the player to see what locations at which an item can be built using the same interface for researched and un-researched items, and lets the player quickly compare the cost and build times for them on the production screen, without having to open a separate 'opedia screen. Also, we don't have an 'opedia yet, so it's sort of the only option at the moment.
Why present the player with 500 options in early game if he can only choose 10?
The default setting should be to display only available items. Having to specifically toggle un "unavailable" or similar items should make it clear what's going on...
If these totally-unavalable items are included it needs to be obvious. Perhaps they can be more strongly grayed out.
Rather than, or in addition to, degrees of greying, what about alternative ways to indicate these things? Perhaps there could be a column where available and buildable at the selected location could be shown with a green checkmark icon, avaialble but not buildable at the selected location could be a yellow circle or yellow triangle, and not available could be a red X, or similar?
Also we can't have the buttons replacing the column headings. Columns of numbers need headings.
I agree, and the buttons weren't meant to be the headings.
Also headings are great for sorting lists, by clicking on the headings to sort by that field.
I agree, and I considered making a sortable-by-column heading listbox control, but doing so is rather non-trivial and I had and still have lots of other things to work on... so it will likely have to wait a while.