You can add sugar in the same amount as the honey and cook it until it’s thickened into a syrup. The original recipe is thin because of the honey, but the sugar would need to cook some to dissolve in the liquid.

The liquid will be watery since it’s essentially a tea with added honey. It should still be fine, but it won’t be quite as potent as a batch where the liquid was squeezed out of the berries.

It won’t have the same beneficial health benefits since it will no longer be raw and it may turn into a very thick syrup or overcook by the time the elderberries are done. If you don’t cook it too long though you’ll still get the health benefits of the elderberry and some from the honey, but it does have to be cooked well enough or the elderberry can cause digestive issues.

Shelf life and storage information is available in the FAQ under the recipe.

As long as you end up with about 3 cups of liquid (since you doubled the recipe) it should be ok to add more water.

When you do the pressure release the steam will vent out and the liquid will reduce some. You can also continue to cook it some on simmer with the lid off for a bit if you want to reduce it down some more before adding the honey.

The amount of fresh berries used in the recipe isn’t the same as the amount of dried berries but the water is the same.

Heating the honey destroys some of its health benefits. This recipe is much thinner than a traditional syrup, but you could reduce it down with the honey if you prefer.

You can freeze it for a longer shelf life. An ice cube tray would work well.

Since this isn’t specifically a canning recipe, and because the sugar content (a preservative) isn’t as high as a canned jelly or jam it may not work well for canning.

Yes. You can also freeze it in small servings, like in an ice cube tray.

Either will work, but herbs generally last longer if stored in the freezer.