Thanks for the quick answer 
But i think that i didnt understand you in 100%.
I have vc_#1 and it connected to the vro as instance and also as extension. If i want to run my workflows i can do it from the web client of vc_#1.
Now, i want to run the same workflows from the same vro from different vCenter (from the web client), lets call it vc_#2.
I connected it the same as vc_#1, as instance and as extension but when i log into the web client of vc_#2 i cant connect the vro extension..
From what i understood from you, you gave me a solution to use the objects of vc_#2 in vro workflows.
I want something a little bit different. As i said i want to run the workflows that i wrote from the web client of two different vCenters