boa.chain(...) =  boa.chain.subset or 
  boa.chain.collapse. While work.sync = F, only the master
  list will be updated if MCMC sequences are added or deleted. A call to
  boa.chain.reset will reset this variable to T and copy the master
  list to the working list..boa.chain.
If boa.chain() is called with either a list as the single argument, or with one
or more arguments in the  =