Let me know if you find a solution. Irritates the hell out of me, too.
I moved to the Aera 500 from a Lowrance Airmap 500 which, apart from colour, was superior in every way. Sadly Lowrance stopped providing database updates and then I had screen problems, or I'd still be using it.
What I do is use Google maps to pick a suitable place (1 High Street often works) in any town I want to use as a waypoint.
Also, a small word of caution: using Skydemon Light to plan routes then uploading to the Garmin results in the Garmin failing to recognise that,e.g., an airfield is an airfield - you get a waypoint in the same place but without the 'special' features like runway extensions, radio frequencies &c. I usually manually plan the route now, or plan in Skydemon Light but then edit on the Garmin.