With regards to Actions Prompt cell, VBA won't barf over it, but, it does nothing.
@Surrogate: tried your code in V2019 and saw now visible results. Certainly no visible behavior. Only the bones remain.
@Vojo: Sorry. The discovery, itself, is what's "new". What was discovered was quite old. Archeology at its best.
Prompt Cell (Actions Section)
Beginning with Visio 2002, this cell is no longer used.
Remarks
In earlier versions of Visio, this cell specified a descriptive prompt that appeared in the status bar when you selected the corresponding shortcut command.