We have a gingerbread recipe calling for potassium carbonate (vulgo baking potash). One year I replaced the baking potash with baking soda 1:1. It worked fine.
Later I researched what the supposed differences are and found a claim that you may leave the dough up to several days in a cool place to rest when using baking potash but not when using baking soda. The (family) recipe originally also allowed to substitute baking potash for hartshorn salt (ammonium carbonate), but since this has the effect that the dough gets a little runny in the oven and therefore the resulting gingerbread is flatter than desired, we haven't used this in decades.
This answer describes potash as "purely historical leavener". Alas, where I come from (Germany) it is commonly used in Christmas recipes. In fact you will find it alongside the respective spices during the season.
The recipe of my family explicitly allows for storing the ready dough in a cool place for several days. Another recipe of the family of my significant other actually calls for leaving the dough in a cool place for several days and also uses baking potash. I never thought anything of it, but "the internet" appears to ascribe preservative properties of sorts to baking potash.
Or is there something else behind the alleged difference in keeping the dough in a cool place? For example, is baking soda perhaps known to somehow dissolve or otherwise react with the other ingredients and thereby lose its leavening effect?
Could someone please shed some light on the properties baking potash would have in a recipe aside from the leavening effect?! Please provide authoritative sources, if possible.