Sorry I keep making all these issues. I'm trying to convert a ton of old scripts to Typescript and finding all kinds of fun things.

One is that in the AE api, there is a kindof shorthand when dealing with Properties.

For example, you can create a "Checkbox Control" property:

var p = layer.effect.addProperty("Checkbox Control");

And you can manipulate its sub-property "checkbox" like this (which doesn't work with current typings):

p.checkbox

or, you can do it like this:

p.getProperty("checkbox")

To get this to work in Typescript, you'd need all of AE's effects in your typings, which is a heavy order considering that none of this is documented.