Increase fade in/out from/to black time in iMovie 10.1.4? Is it possible to increase the length of time that the fade in/out from/to black takes when editing a video in iMovie (added using the Settings pop-up menu in the video timeline(?) panel at the bottom of the iMovie window (apologies if I'm not using the correct terminology))? 

(I have to say that I don't find the iMovie interface particularly intuitive and that it seems to be a little fiddly to try to change effects once you have added them to a video. I tried searching, but I couldn't find anything in the Help about this.)
No, you cannot change the fade time in Settings &gt; Fade Out to Black.

Even the manual Transitions &gt; Fade to Black does not work well because it fades to black too quickly (in about 1/3 of the duration of the transition), then it's black for the remaining 2/3 of the duration.

If you want a linear fade to black that you can set the duration, just add a Cross Dissolve to the end of the timeline and set the Duration of transition.