@Neosaiyan7 Omni-Manifestation isn't summoning things, it's manifesting yourself into existence (or rather, totality) as anything you want.
I would say it can generally be considered as a secondary/complementary power to powers like Absolute Transcendence, Indeterminacy, Omnilock, etc, as a way by which they can interact directly with (or appear within) totality despite being so far beyond it. They can manifest themselves as literally anything within totality, from normal people to entire realities, concepts, etc. You could also think of it like an in-verse version of an author making a self-insert character.
In any case, for the question posed by this post...
Here's the current definition of the Omnipotence Derivatives category: "Aspects, expressions, forms and variations of Omnipotence; i.e., powers representing fundamental qualities, overarching capabilities or different ways of being Omnipotent, and powers that are Omnipotent in their own right."
I don't think it is Omnipotent in its own right (in this case, it is meant in the sense of powers like Arcanepotence and Scientiapotence, which are explicitly stated to be Omnipotent in nature), or a unique way of being Omnipotent. It could be a fundamental quality, I guess? Or an overarching capability?
But like I said before, I think it mainly comes as an accompanying power to powers like Absolute Transcendence, Totality Embodiment/Unity, Indeterminacy and Omnilock, and primarily makes sense in the context of such powers. After all, if you only have Omni-Manifestation, then what are you when you're not manifested as anything? 'Manifestations' imply that there is some greater or abstract thing being manifested, but Omni-Manifestation gives no indication of what the user's 'greater' state is.
Because of this, I don't think Omni-Manifestation could be said to be an overarching capability of Omnipotence. However, it could be argued to be a fundamental quality of Omnipotence, in the sense that it represents the capacity of an Omnipotent being to appear as anything or anyone at any time or place within totality despite being so far beyond it. Or you could argue that it's not as fundamental as powers like Omniscience and Omnipresence, which have long been considered fundamental properties of Omnipotence.
Ultimately, I'm not sure, though I'm somewhat leaning towards it not being an Omnipotence Derivative, primarily due to the fact that it seems secondary to several other Omnipotence Derivatives.