I could not agree more with @Jose…
…@mikshaw, I always thought the same about you. 
Keep the good things coming!
I would like to share something for the post #3195 written by @jose about “EXPORT: Possible solutions”
When he mentioned:“make sure that the files ffmpeg.exe, ffplay.exe and ffprobe.exe are present in the plugins directory”, I realized that the last “Pencil2D 0.5.4b” file (which can be downloaded here) does not have a plugin folder nor a file called ffmpeg.exe.
What I found was that an old version of Pencil had a folder called plugins with the ffmep.exe file. Searching the Internet I found this Link in which you can download the full package mentioned by @jose (ffmpeg.exe, ffplay.exe and ffprobe.exe). This link is only for WindowSystem, but in the same page go to download and choose your OS accordingly.
If those files are needed I was thinking to mention here about adding a proper plugin-folder with those files inside, to the “Pencil2D-dev-0.5.4b-win.zip” presented on the nightly builds.
EDITED: the correct page for downloading ffmep.exe to your system is here