Hi, not sure I fully understand, you should not copy and paste flows or processes across different openLCA "databases",
but you can use ecoinvent and PSILCA in parallel if you adjust your LCIA method, and you can export your foreground LCA model as JSON and import into another database, or also merge two entire databases. For merging, you should add the smaller database to the larger database, so e.g. ecoinvent unit process into PSILCA.
Hth, Andreas