An exdx file extension is related to the Testbase Online format. Seems to be obsolete format.
EXDX file extension - Testbase Online format
What is exdx file? How to open exdx files?
File type specification:
The exdx file extension is associated with the Testbase Online format.
Most likely some old data format without support from the developer or producer. No further information could be found.
This exdx file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.