How can I create a Bowen knot? The Bowen knot is used on Apple keyboards as the symbol of the ⌘ Command key, also known as Viking's Shield, Heraldic Knot, etc.
I'm trying to work out the overlap. Ideally, I want to use a Bézier curve which can then be modified in various ways using circles or planes for various end results. I guess I can use either a screw modifier or a modified spiral for the end circles, because they must either tilt up or down accordingly depending on the flow from one corner to another, right?

The flow from one corner to the next is pretty straightforward. As simple as connecting vertices. It's the end curves I'm having trouble figuring out.
How can I create a Bowen knot?
From left to right:

Create a circle and in edit mode shift it

Delete a quarter of the vertices

Duplicate/rotate 3 times

Join the vertices

Rotate each circle (say) 10 degrees

Convert the mesh into a curve



Curve settings:

Give it extrusion. As the extrusion is along Z, rotate the knot around X so that it is Z up and apply the rotation.
Shader: get the U of the UV that is along the curve and add a color ramp.
a better, quicker way

Start from a plane instead of a circle.
Add subdivisions.
Next steps are the same.