Steps to reproduce

1. Open an incognito window.
2. Reduce size of window so not all columns of the pages app would fit (ie 300 pixels)
3. Open pages app
4. Notice columns are too small to fit content.

This happens even more quickly when dealing with content apps with a lot of columns. Those wil make the jrcName column completely disappear in the treeview. Unless one specifies minimumWidthFromContent: true on the column

Also checking the code of info.magnolia.ui.contentapp.configuration.column.ConfiguredColumnDefinition shows that the value is by default false.

https://docs.magnolia-cms.com/product-docs/6.2/Apps/App-configuration/Column-definition.html claims minimumWidthFromContent is true by default which is incorrect.

Workaround

explicitly specify: minimumWidthFromContent: true on columns that need to be visible