Jens,

Changing the friction coefficient in the Configuration only affects "new restraints" that you add to a model. (You wouldn't want this option to change all the supports for all existing models in the directory - right?)

As OG stated, you can scale the friction coefficient used by adjusting the friction multiplier on the "Load Case Options" tab of the "Static Load Case Editor".

But, if you actually want to change your input values of the friction coefficient, the most efficient way to do this is to pull up the "restraint list", and just go down the "Mu" column, adjusting the values.