I lost sight of the check boxes above the Custom Column selectors, or they hid themselves
I thought one could add filter selectors for custom columns similar to those for Author, Title and Publisher - I know they're available via the context menu, but the filter selectors are more visible.
Could you display custom dates according to the format specified in the custom column. I have columns where I only make use of the time segments, so what ends up in the date segments is arbitrary, and for me the timezone is almost always totally irrelevant.
I doubt you can do anything about this, but might as well ask: if you scroll the library options panel with the mouse, its very easy to inadvertently scroll one or two of the Custom Column dropdown selectors to another value. Don't use the mouse wheel to scroll is the obvious answer, but if Save, Save & Exit and Exit had shortcuts such as Ctrl+S, Enter and Escape there would be less need to scroll. I wouldn't even mind if you ignored the scroll wheel on that dialogue, but I suspect that's not easy and others might not like it.
BR