I have a partial version of this macro working, without xparse, but I needed to tweak it and it got too unwieldy, so I'm trying to use xparse instead. It's admittedly a farfetched macro, but I'm ...
In an answer to Flushing PGF commands and local variable Matthew had suggested using \IfNoValueTF within a TikZ \node specification to determine the text. This solution works great for me. However, ...