Let's assume that, for some arbitrary reason, helicopter blades are too long for transport or storage. Folding them at the rotor hub, as is done with conventional folding helicopter blades, would still be too long and there is a need to fold them further. So, they are folded somewhere in the middle of the blade instead (or as well).
Do such folding helicopter blades exist? If not, has there been theoretical studies on how it could be done? What would be the impact on blade performance?
This is a question about the theoretical feasibility and difficulty of using such folding blades, and whether there have been existing studies or designs for it. As such, the practical applications and whether it would be worth it, or whether there would actually be a real-life scenario where this would be useful, should mostly be ignored.
(Bonus point if it is possible to deploy the folded blades simply by starting the engine, but this is probably too outrageously complicated to pull off anyway.)