There is nice feature in this forum that allows modern browser (such as latest Chrome, Mozillla Firefox or Safari on the Mac) to notify you of events that might be of interest to you (e.g. someone mentions you in a topic, or someone replies to your post).
In case your browser supports it, it will display you this message:
You need to click Allow to start receiving notifications.
Then you just let OG browser tab open and can browse other sites and you will received notification even if Overgrow tab is not the active one.
Notification is shown on the side of the window and looks like this:
Clicking on the notification will bring you to the browser’s latest Overgrow tab you have open. 
Disabling / reenabling notifications can be done in user’s preferences (Your avatar in top-right corner -> 
) again.