Changing the synonym type from unidirectional to bidirectional is not working. After saving the change, it'll be returned to the previous type.

Simulation

• Create a unidirectional synonym with terms in both fields and save.
• Edit the synonym type to bidirectional and save.
• Go back to edit the synonym and note that it's still unidirectional but with the terms from the second field copied into the first field.

Workaround

Manually erase the second field ("What the search returns in addition") before changing the type to unidirectional.