this._createHierarchy is not a function

literally changed existing (working) code for a column to “tree” and I get this error… a Pro thing?

Most likely that you have the code wrong - it should be “stree”: … likecolumn

“tree” column converts Grid to TreeGrid, be sure that you are using PRO version of DHTMLX and the related files were included ( you need to include full suite or to include treegrid.js file separately )