Perhaps new manifold tool ( manifold feature , radian ) should support this like Qgis !!
Q doesn't support this natively, nor does Q have any routing capabilities itself even with a plug in. There's a plug in you can integrate in for one of the services, but that simply is using Q as a browser to connect to a web service which actually does the routing.
I make those distinctions for two reasons:
1. Using a web service is different than doing your own routing. If you use a web service the feature only works where Internet works - not so good on a truck crossing Poland on your way from Paris to Vilnius when you are in a dead zone, or for that matter crossing many parts of the Southwest in the US away from interstate highways. Another issue is handing over your personal data and location to third parties: Many people also don't like how supposedly "free" web sites in fact harvest the data you provide for resale to others (Strava being a famous example). If you don't mind becoming the product that is being sold, and passing yet more info about yourself into the data mining advertising/profiling leviathan, sure, such sites are "free."
2. Not everybody wants to play software integrator, even if the effort required is low, at least at first. Whenever it is up to you to install modules from different groups, which themselves in turn are pieced together from yet other groups, it is up to you to choose wisely for the first installation and then you take on the maintenance task of resolving version skew issues as the various players zig and zag. That's not for everybody.
So no, Manifold won't require people to do that. Instead, whatever Manifold does, whether it uses an external service or uses direct contact to OSM, it will all be built in from one source, directly connecting, the way Manifold works with imageservers and other web servers (WMS, WMTS, TMS, WFS, ArcGIS REST, etc., etc....) and very, very many data sources.
My own view is that using external services is something that is not too terrible (let's face it... if you are using Internet you've long ago given up any hope of privacy) so reaching out to things like OSRM or similar is absolutely an OK idea, very analogous to offering a large roster of web servers for imagery and feature data. In fact, while it would be important to offer at least one fully integrated such service I can see that offering a roster of router services would be great so that people can pick and choose which one they prefer.
I suppose at some future point it would make sense to provide direct routing, either routing within the desktop against OSM or other data resident on a server, or against fully local, downloaded data. Most long distance travel is on major roads, which are relatively small networks. You can easily fit an entire continent, even Eurasia, of major highways and major secondary roads into a Radian project.