The great text editor iA Writer has introduced content blocks with a new syntax (https://ia.net/writer/support/general/content-blocks#toc):
Simple example
/transclude.md 'Example link (title/caption is ignored for text file types)'
It would be nice to see a standard syntax emerge for transclusion. Such variation in syntax is frustrating and creates lock-in to specific tooling. As pointed out by @jmatsushita, one of the reasons hercule uses a precedinge colon is that it degrades to standard link in environments that don’t support transclusion, reducing the lock-in.