Soy sauce in lieu of salt, for pretty much anything liquidy. Gravy, soup, pasta sauce, what have you.

100%! Why have just salt when you can have salt and umami!

I also put a little soy sauce in the beaten egg mixture for omelette or scrambled eggs :)

because soy is such a dominant flavor, that’s why. it tends to over power everything.

Your mileage may vary i suppose. Soy doesn’t seem to be a problem for Japanese cuisine, which I usually consider as tasting very light in comparison to western food.

Tamagoyaki egg rolls for example use soy sauce and are delicious and not overpowering at all.

justonecookbook.com/tamagoyaki-japanese-rolled-om…

because it’s a condiment in Japanese cuisine, not an ingredient.
Did you see the recipe? It’s mixed in together with the egg before you cook it.