Any way to have "hidden" status effects?

Tokens all have those little convenient markers, generally i use them to track hunters mark, poisoned, prone, etc, but is there anyway to make them hidden to players? For example, marking certain npcs with a colored dot if they have a key on them, but I dont want the players to be able to see that colored dot and I dont want to just draw on the GM layer because these tokens will be moving around. 

I either make a note on an open text file or physical note pad. I also make one of the available token auras visible to me (the GM) only so that it's available to me for that kind of thing.

No as-far-as Status Markers  But, yes with Token Auras, for a workaround that could achieve the same ending. (Like Rick said). Auras can be set to be seen by GM-Only (uncheck SEE and EDIT). It's an Aura of color, not an icon, but you could potentially use it if you don't already employ Auras for something else. For example a GM-Only Green Aura could tell you that NPC has Poison skills, and a Yellow GM-only Aura could tell you that NPC has a Key.