I really like the first part, even though for a high number of edges and/or corners, the number of different wang tiles is going to make this unwieldy. However, I think it isn’t a problem because it could probably be combined with the option to draw single colors as done in the terrain editing mode.
The second part where we allow flipped or rotated versions of the tiles to get a wang pattern assigned seems a little complicated. Alternatively, I just thought that maybe we should add some buttons that change the display of the entire tileset to be flipped or rotated, in which case you could paint on the flipped/rotated version of the tileset just like you could on the regular version. These buttons could even be made available while editing the map as well, to allow picking flipped/rotated tiles directly from the tileset.
In any case, it’s awesome to see the first parts of this tool working and it looks very promising!