I know you stated you're looking for remedies *beyond* diet, but it is very difficult to look the relationship between blood glucose and insulin and not regard dietary intake, which directly affects glucose metabolism in the form of carbohydrate consumption. Even cutting out "simple white" carbs isn't enough for many people. "Complex" carbs are still broken down and converted into glucose which still gets dumped into the bloodstream, causing a rise in glucose and a subsequent rise in insulin; this process is much more marked during the insulin sensitivity of pregnant metabolism.
Â
When carbohydrate intake is drastically lowered, you are not dumping glucose into your bloodstream, preventing insulin spikes and thus preventing the conditions that make GD possible. Glucogenesis still happens from consumed protein, that is whatever glucose your body truly needs is manufactured from the protein you eat (this is why some diabetics still get elevated glucose readings in the absence of carb consumption). It isn't true that you "need carbs for energy," glucose is burned for energy because the body has to do something with it (burn as much as immediately possible and use insulin to store the rest in fat cells) or else high levels or circulating blood glucose will wreak havoc on the body.
Â
Sorry for the small lecture, especially if it's not what you were wanting to hear 
. With the herbal route, I know that true cinnamon (not cassia) has properties that may help with the onset of escalating blood sugars, but it is not recommended during pregnancy, and I have found even one source citing that it is a uterine irritant and could possibly help bring on contractions. Best of luck to you 
