OK, I'm not completely sure I understand your post, but I'll try anyway.
If you mean that the 4-sec greenscreen shot is the same shot
repeating istelf every 11 seconds, just do the greenscreening once and copy-paste the clip multiple times in your editor after having been rendered.
If you mean that it's a different shot
every 11 seconds, than this is what you should do:
You see, CompositeLab works with layers. You do the chroma keying, then take the picture/video from the 'Media' tab in the toolbox and literally put it under
So if it's a picture you're using as a background, then you only need to put it once on the timeline, under all your chroma keyed shots, and make it last the right amount of frames. You cannot do this, however, if the shots in-between your greenscreen shots are also
using a greenscreen. In that case, you would need to crop the duration of the background to fit every individual chroma keyed shot.
And remember: When working in CLab, work shot-by shot, not with the whole movie at once, for then your project will be way too massive.
I hope this was helpful.