Consider the following example:

// load a graph from the RDBMS or from CSV
PgxGraph g1 = session.readGraphWithProperties("path/to/graph_config.json");

// create an updatable copy of the graph
PgxGraph g2 = g1.clone("new_graph_name");

// insert an additional vertex into the graph
g2.executePgql("INSERT VERTEX v " +
               "         LABELS ( Person ) " +
               "         PROPERTIES ( v.firstName = 'Camille', " +
               "                      v.lastName = ' Mullins')"); 

Additionally, there is also a PgxGraph.cloneAndExecutePgql(String query, String graphName) method that combines the last two steps from above example into a single step:

// create an updatable copy of the graph while inserting a new vertex
PgxGraph g2_copy = g1.cloneAndExecutePgql(
                     "INSERT VERTEX v " +
                     "         LABELS ( Person ) " +
                     "         PROPERTIES ( v.firstName = 'Camille', " +
                     "                      v.lastName = ' Mullins') "
                   , "new_graph_name");

Note that graphs that are created through PgxGraph.clone() are local to the session. However, they can be shared with other sessions through the PgxGraph.publish(..) methods but then they are no longer updatable through PGQL. Only session-local graphs are updatable but persistent graphs are not.