You can mark an opportunity or event as a favorite. This allows you to save the opportunity for later on so you can easily apply at a later stage.
Go to the opportunity overview page
In the top-right corner of the opportunity, under the button that says "Join" you will find a star button.
When you press on this, its color will change, from white to yellow. The opportunity has been added to your favorites.
Note: No one else will be able to see this or receive a notification about this
Press on the star button again to un-favorite it
To view which opportunities or events you have favorited, press on the profile icon in the top-right corner of your screen. Then press on "agenda", there you will find your list of favorites.