Preparing an NPC stat sheet

I am preparing a stat sheet for creature that has a bonus action called Chill Breath. This is the description of the action

As a bonus action, the ice goblin can breathe a chill air towards the target. The target must make a DC 13 Constitution saving throw or have disadvantage on the next attack roll it makes before the end of its next turn.

When I put the NPC on the Combat Tracker, it properly parses and displays the action, the saving throw required and the fact that it recharged on a d6 roll of 5 or 6. However, it does not create an effect to be put on the target that indicates that the target has disadvantage on its next attack roll. How do I modify the description so that it can be properly parsed.

There is no wording which will pick up and parse a disadvantage on an attack or anything else. Advantage/disadvantage isn't one of the things that's parsed automatically.

You could just make the goblin give a -4 or -5 modifier on the next attack which is about the equivalent of disadvantage.

I ended up creating a custom effect under the Effects Tool that puts the disadvantage on the target. That seems to work.