Regular quake engines are limited to 256 unique models precached at one time, and with the increased number of weapons and monsters available in quoth, there is a risk large maps can hit the limit.
To allow you to save models for just a little extra hassle, you can now create triggers using a point entity and the mangle field. Simply make a trigger of the desired classname as if it were a point entity with no model. Place so that the origin of the entity is at the minimum point of the trigger, which will be its bottom left corner in each of the three 2D windows of your editor. Set “mangle” to the size of the trigger in units, in the form “x y z”
If you are using worldcraft or hammer, you will not be able to define an entity class which can be both brush based and point sized. To accomodate this, for every trigger in quoth there is an alternative classname with the suffix “_point”. So to make a point entity trigger_once in worldcraft, create a point entity with the classname trigger_once_point. Then fill in mangle and the rest of the fields as normal.