Various kinds of tensor networks might be an example. Wikipedia claims that Penrose’s graphical tensor notation is from 1971. Its descendant, ZX calculus is from as late as 2008. Arguably the first tensor networks were Feynman diagrams though, and 1948 is before your cutoff of 1960. (Actually, now that I think about it, it’s kind of funny that the infinite dimensional case came before the finite dimensional one here.)
Various kinds of tensor networks might be an example. Wikipedia claims that Penrose’s graphical tensor notation is from 1971. Its descendant, ZX calculus is from as late as 2008. Arguably the first tensor networks were Feynman diagrams though, and 1948 is before your cutoff of 1960. (Actually, now that I think about it, it’s kind of funny that the infinite dimensional case came before the finite dimensional one here.)
Relatedly: string diagrams (with Penrose’s tensor notation apparently being seen as a precursor)