Tutorial:

How that works
Pt 1: Technical part
The way it works is pretty simple, To fold the wings in that way

While being in that way

It works on a reliable System Which is on The inversing System
One rotator 'First one' is pretty far away from the Wing, Being in the Fuselage, going 70° Backwards, Making the Wing Going Off the Wing base limit, so there is Two Fuselage parts Making the System acting further away, Then there is a hinge rotator at the end of the fuselage, At the connection to the Wing, Going 35°
Why 35 and 70?
70-35=35 so as the tail is angled 35° It goes perfectly with the tail angling
And i want to angle 35 as being greatly Backwards, So the 35 counteracts 70 as 35*2=70 so 70÷2=35
The Fuselage permits to angle backwards but the Wing will go back because of the 70°

Pt 2
The functionallity
The Actual craft has wings Swept to 35°
As it's hard to explain verbally or written so the 2 pics explains Itself
But I'll try
The First rotator going 70° rotates it, The fuselage permits it to go further, and the second rotator going 35° Counteracts the rotation without counteracting the fact that it goes Backwards
So You Can Say how it functions as simple while being in a long tutorial

Pt 3
Building

The wings are folded and you can see how it works
Represantation:
0------:::[

0=Rotator
------= Fuselages
:::= Hinge rotator
[= Wing starting

Or
Needed:
One small rotator, or normal
Two Fuselage pieces
Hinge rotator

Instructions
Mount the small or normal rotator about at the middle of the fuselage
Or a hinge rotator on The side on The fuselage
Put a .25 fuselage piece on The rotator
Put a longer piece: about 4 units long
Put at the end a hinge rotator that counteracts the rotator so you have the angle you want
Ex: 70-45=25 so it sweeps 25°
70-30=40 so it sweeps 40°

That's it
I Hope you liked that