Edit: Ok I just closed and re-opened Glyphs App, it works like Robofont now, except that the right-most point turns into a corner point, even though I’m holding shift.
When I try to connect a point to a open point that has a control point on the other side it doesn’t let me create a smooth point. Best demonstrated with videos:
Fontlab:
https://www.youtube.com/watch?v=I00dcDkC8F0&feature=youtu.be
Robofont
https://www.youtube.com/watch?v=S2Zx8TaC0jw&feature=youtu.be
Glyphs App
https://www.youtube.com/watch?v=pPwNK6rqSPw&feature=youtu.be
I think the best way is Robofont where you can connect smoothly to a point (which already has a control point on the other side) — the quality is a bit crap — though you can see the bottom point turns into a point with a zero-length handle which is not necessary however.