In your assembly, Click Tools menu and select Equations.
Add an equation (Material Thickness) under Global Variables and set a value and click OK to close the equation.
Right click Annotations in the Feature tree of your assembly and select Show Feature Dimensions
Double click One of the Parts' feature in your assembly (like the notch).
the dimensions will be shown. Double click the dimension you want to change (the height of the notch) and Type
="Material Thickness" * 1.01
Don't forget the quotation marks.
and click OK
now if you change the value of your Material Thickness in your assembly Equation and rebuild manually
all your parts will be updated.