I am looking for an app that allows you to construct multiple-stop itinerary on + in one query :

```
A -- B # What is possible
A -- C -- B # What I am looking for

```

[Google Maps](https://maps.google.com) only allow those by car, foot and bike.  

Both [Citymapper](https://citymapper.com/) and [Transit](https://transitapp.com/) don't support it.

And neither of the local networks' app that I use have that possibility.

Is there an app/website, preferably widespread (local answers are welcome nevertheless), that allow for such itinerary on public transport?

As an aside, I was wondering if there is a technical barrier to implementing such solution?