Sub (/) path operator
The Sub (/) sub operator will return a file within a directory.
It can be used as a binary operator like: parent / "build" that is the build sibling directory of the current file.
It can be used as a postfix unary operator like / "build" that is the build child directory of the current file (equivalent to (me / "build")).
For example:
findit -w '(parent / "build").IS DIR'
Will filter all the files that have a sibling build directory.