This functionality would allow the user to select (through a highlight box, or ctrl+click), only the tools in a workflow they would want to run, and the tools that are not selected would be skipped. The idea is similar to the new "add selected tools to a new tool container", but it would run them instead.
I know the conventional wisdom it to either put everything you don't want run into a tool container and disable it, or to just copy/paste the tools you want run into a blank workflow. However, for very large workflows, it is very time consuming to disable a dozen or more containers, only to re-enable them shortly afterwards, especially if those containers have to be created to isolate the tools that need to be run. Overall, this would be a quality of life improvement that could save the user some time, especially with large or cumbersome workflows.