The Nyingma tradition holds that when Padmasambhava taught in Tibet in the eighth century, much of what he gave was not for that generation. It was written down, sealed and hidden, in caves, in rock, in lakes, in the minds of future people, to be recovered centuries later by revealers called tertons when the conditions were right. The system is called terma, treasure, and it is the mechanism by which the Nyingma school continues to receive new scripture without claiming new authorship.
Yeshe Tsogyal stands at the origin of that mechanism. She is remembered as the disciple who could hear a teaching once and hold it entire, as the scribe who set it into a script she is credited with helping to devise for the purpose, and as the one who did the hiding. In the tradition's own account she is not a passive secretary. She practises what she records, attains realisation, teaches in her own right, and is the reason there is anything left to find.
That gives her a structural position no male figure occupies. Every recovered treasure text in the school, and there are a great many, arrives with her at the beginning of its chain, so a lineage that is otherwise overwhelmingly male passes through a woman at its narrowest point. Modern Tibetan and Western practitioners have made a great deal of this, and the emphasis is not a modern invention: the treasure literature says it plainly.