@Alda Experimenting a little more. Changing the width to 270px makes things work correctly when adding more columns (i.e. four columns fit nicely in my browser window like before, and 5+ adds a scrollbar).

However, the change to flex: "1 0 auto" means that with fewer than ~4 columns, they grow wider. Not super bad yet with 3 columns, but with just the two non-removable ones it looks kinda silly.

Is there maybe some way to set both a minimum and maximum width of columns and allow shrink/growing freely between those limits?