A new system option lets you skip the rebuilding of large assemblies after editing a component in a separate window.
As in previous releases, when you switch back to the assembly window after editing a component in a separate window, a message asks if you want to rebuild the assembly. If you have selected the new option and the assembly is in Large Assembly Mode, then the message no longer appears, the assembly is not rebuilt, and a yellow warning triangle appears on Rebuild 
(Standard toolbar) to indicate that the assembly is out of date.
To set the option, click . Under Large Assembly Mode, select Do not rebuild when switching to assembly window.
As in previous releases, in the rebuild message, you can select to not be asked again and click Yes to rebuild. Subsequently, whenever you switch back to an assembly, it rebuilds automatically without asking, regardless of the assembly size. Now, with the new option selected, this automatic rebuild is skipped for assemblies in Large Assembly Mode.