I think it appears when there are more than two keys [k(…)]. And when I edit it, adding for example enter to the end.
I don’t know why, but I always rather use TypeInto with the keys rather than Send Hotkey, somehow it was always more reliable and also if I use special keys as CTRL+H and so, I can set up DelayBetweenKeys so it can be performed slower for slow systems.
btw - [d(ctrl)]h[u(ctrl)] is a regular way how to work with special keys in TypeInto, but not much documented. I love it though, it gives me power to know exactly what is pressed and typed