While Jamf has never provided a nice GUI way to rearrange the order of the columns, it IS actually possible to control their order, but the way to do it is extremely time consuming and painful to implement. It turns out that the order in which you add the columns to your report is the order that they show up in. In other words, if when going through the tabs when creating a report, if you click on Computer Name, then Last Inventory and then Serial Number or something like that, then your report will get generated in that exact order.
But... it gets even more complicated than this. I've found the only surefire way to get them columns to show up in an exact order is to save your report in between each selection. Yes, you read that right. You would have to click "Computer Name", click Save, click Edit, then click on "Serial Number", click Save, click Edit and then select "Last Inventory" and Save to get them in the order of "Computer Name", "Serial Number", "Last Inventory"
Obviously if you have a report that requires dozens of columns, this doesn't scale well at all. it could easily take you an hour to create a saved report that spits out the data in the order you want. And heaven forbid you realized you forgot to add one in. You basically have to start over. It's why Jamf really should add this in as a feature in some future version of the product. It's WAY too clunky, error prone and time consuming how it works now. And I'm pretty certain this isn't even really a feature, just a coincidence in how the database works.
