You can hide a token from player view without necessarily hiding it behind a Fog of War area. To do so, right-click or click-and-hold a token while using the Select tool. This will pop up the token actions. From here, select Hide.
This will result in the token becoming semi-transparent for the DM, but it will be invisible for all players.
If the token is a combatant, then the same effect will also take place in the Combat Tracker - the token's avatar will be semi-transparent there for the DM, but not appear at all for players.
Hiding tokens is great for encounters where there's a hidden/stealthed enemy, but you still want them to have their own initiative.