In Revit 2019, the data structure used by SOFiSTiK Analysis + Design for Revit for related files has been modified. To comply with the new structure, when upgrading Revit projects from Version 2018 and earlier, the software will resquest to move all project related files under a hidden folder called .SOFiSTiK. This folder is automatically created in the directory where the Revit project (file *.rvt) is saved.