OSE Piping stores dimensions in CSV-files in the table directory in the workbench directory. Edit these CSV files if you want to add new or to change dimensions of the fitting.
A pipe is described by its outer diameter OD, its wall thickness Thk and its height H.
To add new dimensions adjust CSV pipe.csv file.
Wikipedia on Nominal Pipe Size (NPS).
An elbow is described by an angle alpha, outer pipe diameter POD, inner pipe diameter PID, H, J, and M.
To add new elbows, adjust elbow.csv file.
To add new sweep elbows, adjust sweep-elbow.csv file.