There are already some other options in addition to SelectedPath.
There is SelectedPath1, SelectedPath2, SelectedFile, SelectedFile1,
and SelectedFile2.
So, you should be able to do something like:
<Tools>
<Tool Name="DirectorySynchronizer" Path="dirsync"
Arguments="source={SelectedPath1} destination={SelectedPath2}">
<Keys>
<Key>Fx</Key>
</Keys>
</Tool>
</Tools>
Sorry that wasn't more clear. Do you think SelectedPathPanel1 is a
better name than SelectedPath1? It would be easy to change the
variable name. Hopefully at some point, there will be a GUI for all of
the config file values which would make changing the configuration
easier.