We develop TiddlyWiki fairly actively, and so of course there will be a steady stream of new features. Users shouldn’t be alarmed if they don’t understand all of those new features all at once. In many cases, these new features are the culmination of years of thinking and discussion (that’s the case with the genesis widget; the first mention in my notes is 5 years ago).
As others have noted, the trouble is that it’s hard to create examples that are simple enough to understand and yet realistic.
Anyhow, the second example from the genesis widget documentation dynamically creates a div or span element according to the value of a parameter. The only existing way to achieve the same thing is to use a macro with textual substitution. As you know, we’re trying to reduce the need to use textual substitution because of its brittleness.
There is something further that the genesis widget handles which is almost impossible to achieve in any other way: to be able to specify attributes for the widget without knowing their names, values or the overall number of such attributes in advance. This is accomplished by optionally passing a pair of filters, one of which yields the names of the attributes and the other yields the corresponding attributes.
I’d welcome any improvements to the documentation.