Help. Plot freezes after Heist.

The first thing you need to do is make sure the splash screen says "Version F14.6". As I've mentioned in other messages, it's possible to get a partial patching which really screws things up.

That said, you do not need to do the wingman training missions at all. The Wingman Training mission and waypoint won't go away until "Act 2" begins, if memory serves.

Have you completed the League initiation? Have you scrolled through ALL of your waypoints just to make sure there isn't an extra one lurking? Have you heard of "Lucretia's Horde"? Have you looked at your missions in-flight?

Very often, although not until Act 2 if memory serves, you don't get a waypoint at all, just a name. Before I got the "Location Finder" mod this was extremely frustrating, as even though most names are derivatives of the objects they orbit, that object is often a moon whose name doesn't appear on the main map, so that unless you know what planet the moon orbits you don't know where to go on the map. Worse still are the "Santa's Workshop" waypoints: stations with proper names that give NO CLUE as to where they might be. (The North Pole?)

Thanks to the "Location Finder" mod you can look up the name and get a waypoint, which makes those "fly to Santa's Workshop" missions much easier.

Oh, right, back to your problem: your waypoint list is dynamically sorted by distance, which although a real pain in the ass for short-range objects is helpful for finding inserted waypoints: start looking from the BOTTOM.