Storing codes of two external terminologies

¿ How to model the use case of allowing a System to accept for the SAME ELEMENT, TWO DIFFERENT TERMINOLOGIES, that CAN NOT BE MAPPED?
In our use case there is a functional need to record diagnostics either with ICD-10 or ATIC.
ATIC Terminology is used in Catalonia as nursing vocabulary in electronic health record, development of care standards, and data analysis on the provision of nursing care.
The thing is, there is NO MAPPING between both terminologies (at least not bidirectional), as ATIC is more specific and granular. There is a partial mapping from ATIC to ICD-10, but not from ICD-10 to ATIC, as it is not always possible to have a 1 to 1 correspondence.
There are ICD-10 with NO ATIC correspondence.
On the other hand, (n) ATIC could match one single ICD-10. But by doing the conversion you would lose granular information.

So, can you indicate to the implementer something like this?

This would be like indicating / saying ?
Accept values for ICD-10 OR ATIC terminologies. Both are valid terminologies.

Or… are we saying… both terminologies are equivalent / mapped. (Which we do NOT want).

As a plan B we where tempted to do this in the TEMPLATE

But probably this would be modelling based on visualization arguments.
Any feedback or other solutions for that use case would be welcome.