It depends on the meaning of "share" and "import something". Assuming that you want a one-for-one direct replacement of the corresponding artifact in each system, you can consider using ReqIF, but with extreme caution.
1. Ideally, all systems involved should have the exact same type system (artifact type, data type and etc). This means that the types have the exact same UUID, not just their names. This can be achieved by importing artifacts into an "empty" project, or creating a project based on a project template.
2. From the first system, export the artifact(s) in ReqIF format.
3. Import the ReqIF file and create artifacts in the second system.
4. Make changes to the artifacts in the second system.
5. Export the exact same ReqIF definition that was imported at step 3.
6. Import the ReqIF file obtained at step 5 into the first system.
Following the above the steps. The changes of the artifacts can be carried over in a round-trip, at the risk of a messy type system. The artifact Id is definitely different in different systems, as it is kind of "for display" only. The UUID is the true Id of the artifact.
I see no way to keep track of the artifact Id, unless you can somehow expose the UUID.
