The Azure Portal is for a lot of people the go-to place to manage all their Azure resources and services. I myself, mostly use it to verify automated deployments (Azure PowerShell, ARM Templates) or to modify and manage customers cloud resources.
However, sometimes the Portal feels slow without any specific reason and then it is really difficult to find out why. Whenever that is the case there is a keyboard shortcut you can use to check the portal load time of all opened blades.
When you are logged in into the Azure Portal and press the keyboard shortcut CTRL + ALT + D you can see the load time and other useful information for every title.
Pressing CTRL + ALT + D again will remove the portal load information.
Beside this useful keyboard shortcut there are some others you can use specifically for the Azure portal.
To see them all, you can open the Keyboard shortcut help item in the Help Menu on the top-right of the Portal.
Hope it helps!