Have to love the Garmin customer focus.
I also use Navionics from time to time and still have a current annual sub for the app for $89.99.
In July I got 3 emails from Garmin saying I needed to register with Garmin "...if you want to keep receiving emails about Garmin and Navionics products. We've moved all Navionics product information to Garmin.com and we'll no longer send emails about new products from Navionics after 31 July." I haven't registered with them because I dont really need more marketing emails.
I route plan on a desktop PC using OpenCPN (free). You do have to get the chart files for OpenCPN, which cost me 35 euro from
www.o-charts.org/?lng=en for all of Australia including a year's fortnightly updates.
I then export the routes from OpenCPN as GPX files and upload those to my B&G chart plotter via
appchart.bandg.com/core/map