How to change width of last column in Finder
The last column isn't actually a column, strictly speaking, it's a preview.

The only way to resize it is to enlarge the overall window, which can be a bit irritating if you are a lot of levels deep…



You can try Alt/dragging one of the columns smaller, which will change all of them. Then, allowing for a bit of a screen bug which means you need to change the window size slightly, you can gain as much room as possible for the final column/preview

Graphics glitch/screen bug …