is there any 'standard' way to put a visualisation-component on an user interface ? .. the vis.h in the SDK unfortunately doesn't give too much information about this

It would be as simple as structuring your visualization as a child window of your main user interface. As for getting that child window into the user interface, either you need to write your own user interface, or design your visualization as a Columns UI Extension.

hmm
Well, what if I have my own UI and don't want to write a new vis-plugin but put an existing one on the UI ? I fear that's not possible, but can't you give a vis-plugin a device-context and coordinates or simply a window to paint on ?

There's no API to do that. Your best bet is to implement support for UI extension visualizations. Alternatively, you could design your own visualization service and hope for people to support it (not very likely given UI extensions already exist, and supporting two interfaces is more work than supporting one).