where is the chakra system located?

[Plenum]

re: bodies

obviously these extra bodies allow us to interact with higher subdensities of 3d, giving us the opportunity of accessing extra information, qualities, abilities

I didn't quite understand this statement. Perhaps you could clarify?

Ra describes all 7 bodies here.

http://www.lawofone.info/results.php?s=47&v=e&ss=1#8

re: silver cord

On that note, I have never seen this ellusive "silver cord" attached to my body in any way, neither at the navel, heart or forehead; and yet, I was vividly, lucidly awake when I saw/see my body "sleeping" in my bed. No cords. And still I know I am still "connected" to the body.

I have not seen it either. I only surmise it from what Ra says when they took Carla 'out of body' and they used this term. This is also folklore in OBE's.

re: seen/unseen

Yes, but is time/space (the metaphysical) truly invisible or simply unseen to 3D (especially "veiled")? Unseen is Love, intelligengt energy, vibration, consciousness. Yet it clothes itself in light; or rather is manifested through light. And as such, it can be seen.

Why would the energy nexi (chakras) be colord-coded if they were "invisible"?

seen in the sense of 'normal' mortal eyes. You have alluded previously, Siren, as have others, to being more 'sensitive' to these phenomena. Alas, they do not appear 'visual' in my current experience, although the experience of 'energy phenomena' is becoming more palpable of late.