I don't see how this would work from a system architecture perspective. Laserfiche entries aren't "aware" of what workflows are currently operating on them at any given moment. Workflow performs its actions through Laserfiche Server, which is all that the entries "see".

The easiest method of taking an individual document out of its workflow is via its metadata. You can configure the workflow to watch for specific conditions (such as having the "Interrupt Workflow" tag set) and terminate it based on those conditions. That's what we do with one of our clients (we use a metadata field called "Stop sending notifications? Yes/No") and it's actually pretty easy. The nice thing is that you can make it context-specific so that it has meaning to the user, as opposed to "Stop workflows operating on this document" which requires them to know what a workflow is - which they often don't.