Video Editing: I'm unable to trim speed control strip's duration I'm using the Video Editing mode, and trying to apply a speed control effect between two markers; For that purpose, I've managed to change the strip's 'trim duration (soft)' properties through setting the start value as the first marker time value, and the end value as the second one -- Yet, unfortunately, these values doesn't change, whenever I try, and gets always reset to 0.

Why I'm getting such behavior?
Split the clip at the points that you want to stretch, then select this strip. Press shift A key and add an Effect>Speed Effect. Then stretch the strip to your desired length.