Thank you for your comments. I was planning to enter the variable to disable the calculation of TBN.
I did not find information on how to calculate the TBN in Blender too, so i had to reinvent the wheel.
btw. TBN is not my merit - I just translated the the C++ code, which i found through Google.
last month I was on vacation and resting from computer =) So, now i plan to continue work with exporter