This is a request to add the capability to temporarily make nodes and their edges invisible.
The main usecase lies in presentations involving workflows. Showing off workflows in presentations has a lot of benefits: Little extra work (if the flow is structured), visually interesting, direct interaction, great views... But some things are not ideal for this, the main one being clutter. Part of the clutter can be reduced with Metanodes, but not everything. Making nodes invisible would be a universal tool for this purpose, though. You could not only hide things, but also make them visible again part by part to expand on an initial core flow step by step.
A variant would be to make the elements not completly invisible, but to scale them down, which might have some benefits. But layout would be a problem, and as the current layouting system has a lot of problems as it is, I wouldn't recommend this route.
There are other ways to improve the "presentability", but this sounds like one of the easiest ones to do. And it could help Knime as a whole, by improving visibility and exposure to decision makers.