If you are already hard coding your column widths through text mode, you'll have to work on it until it fits. There isn't really guidance from Workfront how to get them to fit. Keep in mind not everyone's monitors are the same either.
If you aren't already modifying the widths of the columns in text mode, you can do that.
https://experienceleague.adobe.com/en/docs/workfront/using/reporting/reports/custom-view-samples/vie...
If you are doing the resizing manually by modify the columns while viewing the report it can get a bit wacky. You'll have to clear your browser cache to get it back to default