You saw that creating node and edge tables in SQL Server 2017 is very straightforward. However, there are certain limitations for both table types in this version. Nodes and edge tables cannot be created as memory-optimized, system-versioned temporal tables or temporary tables. Table variables cannot be declared as node or edge tables. Automatically generated $from_id and $to_id columns in an edge table cannot be updated; you can insert a new edge and remove the existing one. Finally, cross database queries on graph objects are not supported.

It is usual that the first implementation of a new feature has certain limitations. It is also usual that most of them are removed in the next release. We have a good reason to hope that this will be the case with these limitations.