• Define a grammar using a "functional representation"
• Display the railroad diagrams of a grammar
• Display an EBNF textual representation of this grammar
• Validate expressions written for this grammar
• Tag associated tokens with corresponding grammar chunks
• Transform an EBNF grammar into a SRFB grammar format (railroad grammar)
• Validate expressions compliant with the above EBNF grammar

You can

• Test it there
• Browse documentation here

I have started with tabakins railroad-diagrams fork, but a lot evolutions took place then, not only one can display svg railroad graphs but can

• generate the validator
• validate (is the sentence well formed or not)
• get the "compiled" result: which part of the sentence is what?