This function can be used to generate a viewport path for use
A viewport path is a list of nested viewport names.
Character values which are viewport names.
Viewport names must only be unique amongst viewports which share the same parent in the viewport tree.
This function can be used to generate a specification for a viewport that includes the viewport's parent's name (and the name of its parent and so on).
For interactive use, it is possible to directly specify a path, but it is strongly recommended that this function is used otherwise in case the path separator is changed in future versions of grid.