Thanks for joining the thread, blemac. 

There are two ways on how you can adjust the columns on a report in QuickBooks Online. You can manually adjust it by hovering your mouse beside the column header and drag the scale width icon to the left or right or you can adjust your browser's zoom settings. 

For further customisation and adjustment on a report you can consider exporting the report into an Excel file and make adjustment there. 

Feel free to drop a comment below if you need further assistance. Thanks.