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When Navigating inside Primary Navigation it is easier to enter focus mode on your screen reader.
The Menu system works much akin to nested Accordions.
Tab to each option in the list, pressing space opens an accordion, up and down arrow keys navigate the accordion.
Accordions sometimes have nested accordions within them, which can be opened by pressing space.
Any accordion can be exited at any time by pressing escape.
If you are familiar with the options and know where you want to go, you can type a slash or question mark anywhere on the page and type the name of the screen you want to move to, followed by return.