You can do your change of tags (fields) directly in the Tag section of the action window. Select your items, and then enter an expression in the field you want to change.
@Bengi010: If the number of characters you want to remove is constant, just use RemoveLeft() and remove the actual number of characters you want removed. In your example, it appears you want to remove 6 chararacters ("01. - "). I can't tell if your "name" fields actual contain double quotes; if so, use 7 chars.
In the name field, type:
=RemoveLeft([name],6)
and this will perform the function RemoveLeft on all the files you've selected for the field where you've entered the expression.
@Unge72: Same idea as above, but you can use the ListItem() function to return the second component (0 based counting, so you want item #1):
=listitem([name],1, - )