The QuickSwitch is a special component of Geometra, and it houses two very important features: Managing Estimates and Navigating between files.
Adding a new Estimate to a project will effectively give you a clean slate to work from, unless you choose to duplicate and existing estimate. Setting up a new estimate lets you calculate options and additions to your project without the hassle of separating it from your main estimate. Duplicating an estimate is a fast way to test large changes to the project to try and find cost optimisation.
Switching between files quickly while in the middle of working on an estimate is done via the QuickSwitch. You can see the entire structure of the projects Drive from here and using the search field in the top right of the dialog you can more easily find that specific file you’re looking for and switch to it. Switching is done via double click.