Code lets you do the weirdest things - you can't tap into the oven circuit with a separate outlet, but you can install a sub panel in place of the oven outlet, then run two lines from the sub panel, one to the oven outlet, and one to the kitchen plug.

All they care about is that you can't run more current down a wire than it's rated for.

You can buy UL-certified commercial products that intelligently split a 240V outlet to two different loads.[0] They're popular in the EV community for avoiding the cost of a dedicated circuit for charging.

[0] https://getneocharge.com/products/neocharge-smart-splitter

$300 to not have to unplug your dryer to plugin your EV charger.

My house is over a century old, nothing is to code anyway. I'm wondering if I could get away with a 20A 120v line meant for a microwave, and swap the neutral to the other leg and wire it to a type e connector. Type e is 16a so the current is fine, but the insulation was intended to separate 120 not 240.

The insulation is rated for 600v almost certainly unless you're running the original knob and tube, in which case you have other issues to consider.

Each leg of 240 is only 120, so it'd probably work.

Don't do it! But if you do it make sure it's breakered correctly and use a AFCI/GFCI combo breaker.

I went and asked an electrician. With a 240V 15A breaker it is completely to code as long as there is absolutely nothing else on the circuit. If there are lights or light switches it is a no go, and if there are other outlets, they would have to be either removed or swapped to the type e outlet as well. I find it weird they don't have a neutral ober there.