PCB-Investigator offers many mouse tools. Those, familiar with Microsoft Windows, most likely already know, like panning and zooming. Even though you can also select those functions via "Start » Mouse Tools", it is arguably faster to use your mouse: holding down the right mouse button to pan, scrolling the mouse wheel to zoom and clicking the left button to select. So, you can use all three of the most needed functions without having to switch manually via the menu each time. But there are also those mouse tools you will need to select via the menu depending on the situation for example "Select in Rectangle". The crucial difference between the simple "Select" and "Select in Rectangle" not only is in the selecting method (clicking vs. drawing a rectangle around the area you want to select), but also in the amount of components you can select with one action. "Select" will get you the smallest component beneath the point you clicked as well as directly tangent parts (each further click on the same point will toggle through all components of all activated layers beneath that clicked point in order of size from smallest to largest), whereas "Select in Rectangle" will get you every component on every activated layer contained in the rectangle and their tangent parts. If you want to select more than one object, you can do this by holding down the shift key and selecting the additional objects. Please note that a click elsewhere without having shift pressed will result in a deselection of all selected objects, to deselect a specific object keep "ctrl" pressed and select the object you want to deselect.

Another possibility for comfortable and quick deselection as well as many other useful use cases are mouse gestures. Mouse gestures are predefined paths you have to "redraw" with your mouse while pressing down your mouse wheel to trigger the associated function. You can activate or deactivate Mouse Gestures via "Help » Strokes on/off".