‌While doing a pentest, besides using the "Targets" tab to take notes on each asset being tested, there was a need to add some general notes for the whole pentest or project.
The built-in notepad is particularly useful if your pentest lasts more than a few days or if you have several targets that use different networks. ‌
As you can see in the screenshot below, in the toolbar, click on the button "Notepad", hide it from the rest of the Windows or Save the current work. Simple, and useful :-)