Here is a diagram involving the four symbols in the graphic lambda-Scale:
– At the left are used drawing conventions from the preview paper “Local and global moves on planary trivalent graphs, lambda calculus and lambda-Scale“.
– At the right are used drawing conventions from “Computing with space…” page 21.
We can pass from a drawing to another by a graphic beta move.
To me, this looks like
a formula which involves four symbols too.