‘nth of type’ conditions for paragraph styles
In CSS, we can use an nth-of-type() selector to define behaviour for the nth instance of a style. For example, we can make all paragraphs have a first line indent, but use nth-of-type(1) to remove the indent from the first paragraph on the page. This feature also supports (odd) and (even) values for n.
This feature would be extremely useful in Indesign for a range of use cases. Importantly, it would eliminate the need for several styles when typesetting multiple-paragraph block quotes, interview dialogue (indenting/outdenting), drop caps on chapter openings, etc.
For full flexibility, I imagine the feature would offer the ability to clarify the extent of the document sampled for the nth of type condition, ie. nth of type within <document>, <story>, <page>, or <contiguous block of paragraphs sharing the same style>.
The feature could be implemented similarly to Nested Styles, except the user would be assigning a paragraph style rather than a character style.