Wanted to add a 3rd column to some of the contact and account layouts. Tested with just the accounts detail layout using the recommended code in the detailviewdefs.php file in /custom/modules/Accounts/metadata
The process to add additional columns is got to custom/modules/~Your Module Name~/metadata/editviewdefs.php. Look for the ‘maxColumns’ array item and change the value to however many columns you need. Then repeat in the detailviewdefs.php file so they match, if you want them to.
Once you have done that and saved the fields, go to Admin >> Repair >> Quick Repair and Rebuld.
After that, go to the Studio, find your module and you should be able to add fields to the additional columns.
I’m also trying to add additional columns. I changed the maxColumns value and the details and edit views in a custom module. then ran quick repair and rebuild relationships as suggested but I still can only see two columns on studio.