I doesn't look like we have access to the History Maximum in DNN Platform. https://www.dnnsoftware.com/Content/Dnn.Evoq.Content/Documentation/Web%20Content%20Management/HTML%20Pro/Administrators/Setting%20Maximum%20Version%20History.html but it looks like you can do the following: https://dnnsupport.dnnsoftware.com/hc/en-us/articles/360005760794-Increasing-the-maximum-number-of-saved-page-versions