Solution
You can find TestStand crash logs and dump files from the following directories:
C:\Users\<YourUsername>\AppData\Local\National Instruments\TestStand 2021 (64-bit)\CrashLogsC:\Users\<YourUsername>\AppData\Local\National Instruments\TestStand 2021 (64-bit)\NIERDump
Note: choose the TestStand version and bitness that you are using.