Concatenate Grob Names
This function can be used to generate a grob path for use
grid.edit and friends.
A grob path is a list of nested grob names.
Character values which are grob names.
Grob names must only be unique amongst grobs which share the same parent in a gTree.
This function can be used to generate a specification for a grob that includes the grob'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.