MD83FO I always leave it automatic, so my friend doesn't have to push buttons, and use selected speed as necessary.
I prefer to do that too, but not always possible.
if Decel pseudo waypoint is sequenced in heading mode, it will activate at localizer capture or upon NAV capture in approach.
I didn't know it did that in heading mode. But 250 kts on LOC capture, That's a bit sporty isn't it? How do you avoid overshooting and get configured and stable with that intercept speed?
i would never push speed without knowing my managed target on PERF page.
A pilot who doesn't make mistakes - a rare thing indeed ! Good for you.
I've made this particular mistake 2 or 3 times in 10 years.