I had never considered this knot for a drawstring toggle as suggested here. Excellent idea. In this capacity, the fact that it is nearly impossible to untie when pulled tight is a feature rather than a bug.
Seeing this post inspired me to try one other knot -- two round turns on two round turns (what I call the "lazy dog"), which can be tied as a loop or a bend. I expect that other hitch-on-hitch knots might work as well.