After running GNPS feature based molecular networking (see the GNPS export and submit module), go to the results page and download the cytoscape data file (Export/Download Network Files/ Download Cytoscape Data).
Unzip the downloaded file and use this module to open the .graphml file.
IMPORTANT: The import loads all library matches based on the peaklist row ID. Do only import GNPS results for peaklists with the same peaklist row IDs. (Filtering is ok; renumbering is not)