Item sets: What is currently a good tool for modifying them?

As we all know, the new client does not support creating custom item sets, and Riot are not currently planning to add it (at least in the near future.)

So, what is currently a good, safe third-party tool for modifying item sets?

I know you can still load the old client to create item sets, but that's extremely awkward because it only saves and activates the item sets once you actually start a game with the appropriate champion through the old client, which makes modifying multiple item sets extremely painful and time-consuming.

There used to be a lot of tools for creating item sets back in the day before the (old) League client supported it natively, but I don't know if any of those are still around and working with the current (e.g. preseason 7) items.

Note that I am not talking about a tool which pulls down pro builds automatically, such as Championify. I'm specifically talking about a tool that allows you to create custom item sets of your own for your champions - preferably one that allows you to start from the default Riot recommended item list and modify from there.

(I also know that I could edit the files manually, but that's not exactly convenient either.)