is it possible to make a view which shows me all machinegroups, only one specific group should not be included.
I know I can work with "Only show selected machine IDs" but this is not the best way because is isn't dynamic.
CCDaveI actually do this exact same thing. Create a copy of the view you want using the Save As function. Then go into the Advanced Agent Data Filter at the bottom of the view, and in the Group ID box put in "NOT" and the machine group you don't want to include (e.g. NOT *servicelevel.client*). Make sure you do not have an quotation marks or it will not work.
Additionally, if there are several clients you want to exclude you can use parentheses and AND to join them (e.g. (NOT *servicelevel1.client1*) AND (NOT *servicelevel2.client2*))