This is kind of an old thread, but beyond the missing reference types described above, the documentation also doesn’t mention that raw data in descriptors ('tdta') begins with a long integer length, which is then followed by that specified number of bytes.
> For the 'Idnt' element I haven't the slightest idea of what it could be, since I never saw one in an Actions Palette file.
Referening to objects by ID is not tremendously useful in saved actions, because IDs are determined at runtime, but it can be very nice for automation plugins or scripts. Using an ID to refer to a document, layer, history state, or other object has the advantage that the ID is unambiguous (unlike a name), and doesn’t change during the life of an object (unlike the index or offset).
Europe, Middle East and Africa