Upon first opening a parts database dialog, all columns are equal-width. This is rarely a good choice, but it is an easy default. Here's a freshly-opened parachute database:

Obviously, the Diameter, Sides, Line Count, and LineLength columns could all be narrower, while most of the others could be wider. If you go and adjust the column widths to be better, your changes are not remembered when you close the window, and so then when you reopen the window it'll be back to equal-width columns.

Furthermore, if I enlarge the window to actually fit all the columns, that too is not remembered. Each time the dialog is opened it is back to default size.

Both of these should be remembered, and saved as part of app memory, not per-file, because these settings are not specific to a rocket design, but to the user's preferences, and it should be (I think) saved separately for each component type, because each one has a different set of data columns.

Having a bunch of good default column widths and window sizes would also be good, and would possibly negate the need to save the user's changes.