Reduce or leave out the salt. It is not essential to the chemistry of the recipe. I will not speculate on salt substitutes, as that is a health and medical issue, off topic for this site.
The pancakes will then not taste as good, but that is unavoidable. Perhaps you can serve them with a highly flavorful accompaniment, like a reduced peach chutney or similar, to make the entire dish more interesting.
Not sure what kind of advice you expected.
Edit: Based on the discussion of baking soda (sodium bicarbonate) usually used in pancakes: as Kate Gregory points out, there may be alternate chemical leaveners.
Another possibility is to use mechanical leavening, by beating the eggs, fat, and any sugar well until they reach the ribbon stage (probably more than necessary, per Harold McGee, but still a clear indication); at this point they will have the maximum amount of air incorporated. This batter cannot be held, but it should rise reasonably well, even without baking powder.
There are also recipes that use whipped egg whites to leaven pancakes, but they produce a different, fluffier product that may be called Fluffy Pancakes or Swedish Pancakes depending on the recipe.
You can certainly make a home made dry mix for waffles, but it is difficult to make one that will require only water to use.
Obviously, some of the ingredients are naturally a dry powder to start with:
- Flour
- Sugar (if you use any)
- Chemical leaveners like baking powder or baking soda
- Salt
De-hyrdated versions of dairy products are readily available, including powdered milk, and powdered buttermilk, depending on your preference. These can be had from most normal grocery stores, at least in the US.
Powdered eggs are available, intended for emergency storage, or for camping. Much to my surprise, you can even find powdered butter on the market, also intended for emergencies. I cannot vouch for the quality of this product.
With these ingredients you could make a dry mixture which is essentially everything in a waffle batter, dehydrated--to just add water.
I suspect if you are willing to relax the "add only water" restriction that you will get a higher quality waffle. Most home made pancake or waffle mixes expect you to add butter and water, or butter, eggs and water.
You can find specific recipes by googling, although pancake mix recipes seem much easier to find.
Best Answer
80% potassium carbonate, 20% sodium bicarbonate at some concentration https://omnivorescookbook.com/kansui is likely to behave very differently than your sodium hydroxide. Kansui is probably strongly buffered, while your pH is likely to wander. That sort of thing is liable to wreck recipes. I'd find a good how-to online, and make the stuff right.