If you select specific properties in Alchemist and add the descriptor, the generated code will be a getter for that property actually.
Looks like it’s just the normal intellisense/autocomplete of vsc. Those are probably suggestions based on things you’ve wrote before. Typescript has to be installed (via npm or yarn) and then you get suggestions that fit the actual model of the object, given that you have the type definitions for that type of object. Here’s an example of how that looks.
It doesn’t help you with constructing your descriptor though - It just helps me when I’m working with descriptors returned from getter functions.
There isn’t really some UXP specific documentation on all that, but there are a lot of AM examples on the internet and as mentioned, batchPlay is kind of the same just with other syntax. You can look at Old docs and search for “ActionDescriptor” or “ActionReference” to get an idea of what you could do with those:
As you can see, there isn’t much more to it than referencing layers by index, name, id or enum value (target layer, next layer, previous layer, …). In batchPlay that’s done by adding _index, _name or _id to the target object for example.