It would be useful to add the ability to hide custom items in the turn tracker, just as we can hide tokens in the turn tracker by moving them to the GM layer. Why? When using custom items with round calculations to track effect durations the players should not know about. The turn tracker with round calculator is already very useful for effect durations the players know about. A checkbox on Custom Item creation is probably the simplest solution that matches the need, and hopefully it could be hidden the same way token items are hidden when on the GM layer. Scenario 1: bad guy buffs his strength before the players are aware of him. I add "STR buff to Able" custom item, decrement by -1, check "hide from players", set initial value to X. Players are never aware of this buff unless they use a detect ability that can see it. Scenario 2: bad guy debuffs player with Slow. I add "Slow on Baker Rnds" as custom item, decrement -1 per round, check "hide from players" , and then set its initial value to Y I can also add "Slow on Baker" as 2nd custom item, leave "hide from players" unchecked, increment by 1, but leaving initial value 0, Player can then see "Slow on Baker" and can see how long it's lasted so far, but won't see the hidden item that counts down the rounds, and i can delete them both when the counter item reaches 0. EDIT: I rewrote the above to make it more concise.
