Alternative syntaxes for Lisp dialects, some of them indentation-sensitive, have been proposed numerous times over the entire history of the Lisp family. From

Alternative syntaxes for Lisp dialects, some of them indentation-sensitive, have been proposed numerous times over the entire history of the Lisp family. From the start, John MacCarthy believed that Lisp would be programmed using M-expressions and not S-expressions. M-expressions are still quite parenthetical, but have some syntactic sugar for case statements and such. In the second incarnation of the Lisp project, which was called Lisp 2, MacCarthy's team introduced an Algol-like syntactic layer transpiling to Lisp. This was still in the middle 1960's! The project didn't go anywhere; Lisp 1.5 outlived it, and is the ancestor of most other Lisp stuff. In the early 1970's, Vaughan Pratt (of "Pratt parser" fame) came up with CGOL: a another alternative programming language syntax layer of Lisp. Scheme has a "sweet expressions" SRFI 110 which I think was originated by David Wheeler. It is indentation-based syntax. The Racket language has numerous language front ends, which are indicated/requested in the source file with #lang. I think one of them is sweet expressions or something like it. Those are just some of the notable things, not counting lesser known individual projects.