I just did a coolant change on the 300 and wanted to chime in on using the opening in the right side panel to view the coolant level. Depending on the color of the coolant, It can definitely be hard to see the fluid level. Over the last couple of years, I've been using a pen light flashlight pressed up against the fluid reservoir from the opening on the right side, it lights it up like a Christmas tree and you can easily see the fluid level when you press a pen light against the coolant reservoir.
Moto Guzzi Griso 1200, Kawasaki Versys X-300
Harley Super Glide Custom, Honda Metropolitan