Nodes have versions so that future improvements don’t cause your existing flows to break! You may notice a Upgrade Version option when you hover over a node if a new version of the node is available. The following Web Agent Scraper node is version v6 for example and upgrading it to v7 would enable new features on the node.
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Updgrading a node

Each time you drag a node from the library onto the canvas, you are dragging the most recent version of that node. There is no way to go back in the version history once you’ve deleted an outdated node. Only looking forward!