Which version of PMF are you on? There was an architecture change on how statuses are stored (on 7.11) to accommodate localization. On latest versions, take a look at D_WorkStatusList and GetWorkItemStatusList. 

It is not totally clear which case type(s) you want to add the new status to – task, bug, issue?  I’ve seen several customers add new bug statuses and we have done so here in our internal implementation of PMF as well.  You’d need to add the additional status as an instance of field value pyStatusWork in the class of the case type that is getting the additional status.  For performance reasons, the statuses are maintained in node-level data pages, so you’ll need to purge the data pages to see your change take effect.  The data page to purge depends on the case type you want to change, but a search on “D_WorkStatusList” will show you all of them.   Adding a column to the scrumboard and mapping various statuses to the columns is largely controlled by the parameter settings for section pxUMapViewerOuter included in section pySBViewer.  We have not added a column to the scrumboard for the new status.  We considered doing this internally, but found better usability by leaving both Open and Open-Review items in the Open column, but distinguishing them with an icon – see below.