Thanks Rolf. I’ve confirmed this was a bug.
The ListBox header was permanently reserving a large area for the sorting arrow, even when the column was not sorted. Combined with the normal header padding, this prevented short captions from appearing in narrow columns.
This has now been fixed. Unsorted columns no longer reserve space for the arrow, while the currently sorted column reserves only the space needed to display it. Sorting continues to work normally.
The fix will be included in the next Objo Studio release: https://feedback.objo.dev/bug/1269