The folks at Adegle have made a tool for quickly creating slipknots on yo-yo string. I thought this was silly at first, but I guess it could be handy if you are making a huge batch of strings, or if you are a 2A or 3A player who is looking for a way to consistently get your strings knotted at the same length.
The “yo-yo string knotter” is available as a 3D printable file on Printables.com. If anyone ever makes a version of this tool with a built in string cutter, I’ll be glad to buy it from you. I’d love to see a sleek metal version of this tool, sort of like Zipline’s knot-removal tool.