Stephan, What I do is set the top level assembly to Def:Exclude Comp. This has worked well with assemblies containing up 200 part/assemblies, more complex assemblies may need other assembly management methods. Select the simp rep, edit>redefine, select the exclude tab, select the top level assembly in the model tree and it should change to Def: Exclude Comp, select the green check mark. Display the simp rep column in the model tree, Display>Add Column. The items to be shown can be set to Master Rep in the Simp Rep column by clicking next to the item name in the column or by redefining the simp rep and using the include tab then select the item. Any new components/assemblies added to the top level will not show in that simp rep until they are set to master rep. When you use hide in assembly mode it will hide that item in drawing mode. Control display with simp rep to avoid this. Use hide for assembly operations and then unhide when finished with your assembly operations. Regards - Chris