@otfaccounting 

RE: I was still in Multiple Window mode when I resized the whole Item List window to just less than full screen, then resized the columns and they stayed. I'd never done that before. 

Do you mean you never resized the Item window? It's kind of tiny by default & only shows 5 items. In any case, I tried it using its default tiny size (after resetting it) and the columns widths still stuck for me. I wouldn't think the size of the window mattered.

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Oh, I get it! You were in multi-window mode but maximized all of the windows! Something I didn't try. I tried both multi-window 'restored' mode and single-window mode, and both of them seem to work as expected.