Facebook has my previous employer as the Secret Chiefs. Currently it has down that I work at the Gnostic Catholic Church. But it asks frequently "When did you work at the Secret Chiefs." It wants to complete my profile info by knowing when I did the job, that wasn't a job.
The question is weird in a couple ways. One, it's Facebook being invasive so it can figure out how to better connect me to stuff. But for two, the question just looks funny when asked, like if it were a conventional job what would your job be? Are you like their liaison, or agent who goes on missions for them? The page who takes memos from one ascended master to another? What would a job working for them look like? Would they have a big top floor group of offices in a skyscraper? Would it be the 11th floor of a building with an elevator with no button numbered 11?
The real odd part of the question though is the word “when.” Working for the Secret Chiefs is the sort of thing that doesn't have a start and stop, it just is. You might think of it along the lines of the point where you join an organization committed the the Great Work, or to initiation or spiritual development, but that presumes that the Secret Chiefs operate purely through clean cut lines of temporal agency.
Cutting away the mythology of ascended masters, or of a secret continental fraternity of masonic occult initiates, we can approach the idea of secret chiefs in a way that is useful and makes more sense. There are two ways I like to look at the idea of the Secret Chiefs.
The first of these is more temporal in nature. Initiates who reach the third order of initiation, or the Order of the SS would be counted amongst the Secret Chiefs. Now this does not refer to a specific order's curriculum or way of doing things, but rather the specific initiatic experience of unifying the ego of the manifest self with the fullness of the unmanifest divine. Any organization led by people in this state of initiation would be a Fully Contacted order in communion with the Secret Chiefs.
That said, this does not mean that everyone who has achieved this level of initiation is in communication with each other. It does not mean that there is a secret group of initiates playing poker in a hidden temple in the Himalayas and deciding the spiritual affairs of mankind.
It means that anyone operating from this perspective is operating in communion with the Harmony which underlies the universe. Their own individual expression of that Harmony will be unique to them, but it will still be an expression of the same source. So their guidance of their students, or of their particular spiritual order or school will still stem from that Invisible College of Masters even if these Masters don't get together and discuss plans and curricula. There is a unity beyond temporal ideas of unity expressed through corporeal agency.
The other half of the coin is the divine fullness, or the pleroma. In traditional Gnosticism the pleroma is an understanding of god which is unified and transcendent but also manifest and individuated. The ultimate God of Gnosticism is like that of Hermeticism or NeoPlatonism, a non-anthropomorphized non-characterized God who is undivided and complete. The pleroma is the movement of this divinity towards manifestation. This is the collective of the divine forces within the whole. The forces within the pleroma are individual divine beings, but the pleroma itself is a singular transcendent nature.
The unity a master has with divinity is a unity with this element of divinity, the full Harmony of the forces of creation united into a singular coalescent whole. Like the metals and planets of alchemy, iron is the manifestation of a particular force within the world, and Mars is the manifestation of the same force within the Heavens, so the planets and the metals form a bridge expressing the communication of the forces embodied in the stars into the elemental sphere of the world. Masters and the forces of the pleroma share a similar relationship.
So then anyone who is in a system being led by one of these Masters works for the Secret Chiefs right? Maybe, maybe not.
Sometimes people join orders, or become students without fully engaging the Work because it just isn't where they are going, or this particular expression might not be the way they're getting there. So working under that Master might not be a situation where an individual is doing the Great Work.
On the flip side, someone called to the Work, is working for the Secret Chiefs as soon as they begin movement towards answering that calling. That same Harmony which represents a component of the concept of the Secret Chiefs and works in tune with Masters might inspire, and draw, and guide people who might eventually become Masters even if they haven't realized they are that at this point in life. So anyone earnestly engaged in the Work, operating under inspiration from Truth, is in the employ of the Secret Chiefs, even if they don't yet realize they're doing the Work. So long as they continue on that path they still work with the Secret Chiefs.
So in the end, there really is no “when.”