At present, Google does not have an API for their MyMaps service. However, the Minimap Sidebar has been designed to interact with Google MyMaps in a number of ways.
Viewing - To view a Google MyMaps map in your sidebar, drag and drop the kml link onto the Minimap Sidebar (alternatively right click link and select open link in sidebar). This uses the Google Maps API ggeoxml function to display the contents.
Another way to view Google MyMaps map is to copy the kml url and add manually using the add kml toolbar dialog.
Once a MyMaps map has been added, it will be stored in the kml/georss tab, where you can toggle visibility, edit the title, and delete.
Importing - If you would like to import a MyMaps map (placemarks only) into your address list, save the file to your computer, open up the Minimap sidebar, go to the ëtoolsí menu button on the toolbar and select ëImport -> kmlí
Exporting address list items - If you would like to export all of your address list items to Google MyMaps, open up the minimap sidebar, go to the tools menu button on the toolbar and select ëExport All To -> kmlí If you would like to export a selection of items from your address list, use ctrl+click (mac cmd+click) or shift+click to get your multiple selection, then right click and select ëShare Location -> Export as kmlí
Now navigate to Google MyMaps and either in a new map or into an existing map, select Import. In the dialog that appears, browse to where you saved the kml file and upload.