Under the Options menu, find composites. Within this find the composite wall whose various thicknesses you want to change.
Keep in mind that this change will only affect this file. If you have or might want walls with the original wall thicknesses,
make a copy of the composite,
rename it
and then change the layer thicknesses as you have described.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"