How can I effectively shade over bi-folding doors?

There are a few solutions for such a requirement with large projections also possible.

One solution is look at the Markilux Pergola or the Weinor Plaza and Plaza Pro system, the addition of lateral side arms and vertical posts helps support the weight of the cover when extended, also there are no retractable arms.  The fabric cover is motor driven out via the front profile using the side laterals.  Consideration still needs be given to supporting the static weight of the cassette at the rear but there are several self supporting steel and aluminium section solutions.

The Markilux Pergola and Weinor Plaza can have the pitch compromised when used as a sun shade and the addition of one or more adjustable legs (Markilux Pergola 210) allows the cover to be lowered at the front by 30cm in rain to allow the water to run off.    If your bi-folds are in existence, there may be some compromises to be made, but we can talk you through this to ensure you at least have a useable and safe system installed.

You can also self support many of the various retractable awnings available using a goal post arrangement although this can be reasonably costly to carry out.