Enable adding tools to a workflow that already run without having to run it again

[josepaez]

I find myself constantly in a situation where I am building a workflow and need to add a browse tool or branch out from the main path to test some ideas or check something and it is very annoying having to run the whole process again, I know that there is the option to cache but it the criteria is very impractical because you can't cache at different points in the workflow easily.

It should be possible to add some tools like browse or output to a file without having to re-run the whole workflow again.