The system tray in Windows 10 is accessible without an add-on. Use the Windows+b command to move focus to it. There are 2 parts to the system tray and when it gets focus, you land in the “User promoted notification area toolbar”. This shows the icons you have chosen to display in the foreground and you use left/right arrow keys to cycle through the icons. You will encounter an icon announced as “Notification Chevron button”, press spacebar to activate this, then press left arrow. This opens the second part of the system tray which is the “Overflow Notification area toolbar” and it contains the remainder of the system tray icons, I.e those you did not elect to show in the foreground. Use the left arrow to move through these icons and you will eventually wrap around to the foreground icons again.
Earlier I said that you decide which icons appear in the foreground User promoted area and the background overflow area. You set these in the Settings app (Windows+I) using the Personalisation category, Task bar sub-category, then use the link entitled “Select which icons appear on the Task bar”. From the list, check the toggle button of items you want in the foreground, unchecked items will be made available in the background.