Thanks Magnus but I already found those before.
There isn't any details about the practice. Somewhere I found that it involves generating oneself as the deity and also visualizing the deity outside of oneself but that's all. And I can't buy the text since I don't have the empowerment.
Padma Lingpa's terma. It's in Rinchen Terdzo vol.23 (Dege version) and has a comparatively short text among all Avalokesrivara texts in Rinchen terdzo.
Generating self and front deities is not rare. Usually you need to generate both when doing longer practice text. In shorter text it's sometimes skipped but it can be either 1. you don't need to generate front mandala or 2. you need to, just the author felt that you should have known it. Depends on what text you are doing.
It's mentioned in Nyingma generation stage teachings. There are several books available.