I was a Google Summer of Code Student for Galaxy Project for the year
2013. One of my main tasks was to implement 'nested workflows' for
Galaxy. See 
This took me more time than I had expected and after sending a
declined PR(See ) I re-attempted something similar with PR# 370.
Through, few off-the-list discussions it has been decided that #370
would be declined as well. However, since this was a feature that was
'in-demand', I thought I would share it here, if in any case somebody
finds it useful. The code is here.
However 'galaxy-central' is soon going to have a similar feature
implemented soon and as such my code might not turn out to be so
However if you happen to find this useful and come across any bug(s)
(apart from that listed on the PR) please feel free to report it.