Render extra controls with some entries

Nice tool, thanks for providing it.

I'd like to have the ability to attach other controls to some of the items in the TreeView - one or more buttons that allow you to operate on the entries. I guess I can probably do this with some of the customisation options you've suggested but it's not that clear to me and some examples would really help. It would also be great to add some CodePen / JSFiddle examples which I always find super helpful to get up-and-running with a new module like this.

Just a few suggestions :)