@abedtash_hamed and @Dymshyts,
SOLOR integrates SNOMED, LOINC, and RxNorm into one common terminology model (not sure if terminology model is the correct term). And can be used to extend the terminology. Something that is being proposed in this thread. On paper, this looks to be a good tool to support the extensions. Also, SOLOR is open source, if there is a community behind SOLOR with the same ICD-SNOMED problem, then maybe all the extension work won't have to fall on the OHDSI community.
We also have concerns about using SNOMED. We have not started using the OMOP CDM, so we have not done an assessment on the ICD to SNOMED terminology mismatch and subsequent patient additions to cohorts without the specified ICD codes. But the reality is we live in the American extension of the ICD world.
I haven't tried SOLOR or Protege.