Actually, just realized that the issue could be solved by adding Transformation (KTR) as a resource. In this case, one can use the File-Resources menu selection. In the dialog select the transformation you wish to import and pick text/xml format. Give the resource a name and save it. You must save your PRPT file again (File-Save).
The caveat here is that transformation should be in the same folder as PRPT file. Then in the data sources, don't select transformation via folder path, but use the name of the resource that was assigned during the previous step (there is no drop down menu for looking thorough the files). You have to know exact name of the resource in order to do so.
