Allow underscore as an "anonymous indentifier"

[Hi-Angel]

Proposal

Not every block in the diagram has to be referenced. For example, given this one:

flowchart TD
   subgraph FOOES
       FOO1["Foo description"]
       FOO2["Foo description"]
   end

   subgraph BARS
       BAR1["Bar description"]
       BAR2["Bar description"]
   end

   FOOES --> BARS

FOO1, FOO2, BAR1 and BAR2 are unused. So reading the sources would be simpler if the variables weren't created, because it becomes immediately clear which parts don't have any references to them.

In modern programming languages that's usually achieved by replacing the identifier name to a underscore _. However when doing the same to the diagram above, almost every block just disappears from the diagram:

flowchart TD
   subgraph FOOES
       _["Foo description"]
       _["Foo description"]
   end

   subgraph BARS
       _["Bar description"]
       _["Bar description"]
   end

   FOOES --> BARS

flowchart TD
   subgraph FOOES
       _["Foo description"]
       _["Foo description"]
   end

   subgraph BARS
       _["Bar description"]
       _["Bar description"]
   end

   FOOES --> BARS

Loading

Example

flowchart TD
   subgraph FOOES
       _["Foo description"]
       _["Foo description"]
   end

   subgraph BARS
       _["Bar description"]
       _["Bar description"]
   end

   FOOES --> BARS

Screenshots

No response