Hi Damon thanks for posting in the Lucid community! We don't formally support imports from pgAdmin - if you'd like to see support for this in the future our development team would love to hear more detail about your use case in the Product Feedback space of this community. Apologies for the inconvenience and thanks for your request!
However, depending on the output of your database with a bit of reformatting you may be able to import your data into Lucidchart using the PostgreSQL, option which we do support. I’ve provided a sample PostgreSQL output to this post, which you may use as a template!