We will not settle the issue here, but the following may be of some help in the discussion:
Hebrew Transliterated
Jeremiah 1:5 BTUrM 'aTShVUrK BBTN YD'yThYK VBTUrM ThTSh'a MUrChM HQDShThYK NBY'a LGVYM NThThYK.
Young's Literal Translation
1:5 `Before I form thee in the belly, I have known thee; and before thou comest forth from the womb I have separated thee, a prophet to nations I have made thee.`
While it may be comforting in some faiths (not just Mormon theology) to believe that Jeremiah existed timeless prior to his conception, the text in the language God ordained to converse with humankind does not support that notion ... it also does not contradict that interpretation. But the text gives us a few clues which may also be found in the English nuances.
There is a progression in the message: Yahweh says to Jeremiah that He knew OF (have known, past perfect) him even before He 'form' (present tense) him in his mother's belly ... the Creator is sharing His perspective abilities with us, in that He can 'look down' through time to come, even before it is arrived in our experience. The language verb constructs tell us that. Yahweh positions Himself by the first phrase 'Before I form thee', then positions Jeremiah with 'I have known thee'. Young makes literal translation of the verbs. That is not a mistake, it is a clue as to Yahweh's perspective OF time from a position greater than but including, and Jeremiah is then located 'in time'.
We cannot answer here the notion of what is dimension time as related to the spiritual realm, but it is a fair statement to say that the Creator of time is as at least as much and most likely far more than time. As such, anything created from His perspective and communicated to us will have a temporal 'location' associated to it for our perspective benefit.
Here are the implications of two possibilities:
1) Jeremiah existed in spirit prior to being placed in a body and soul of life force; we have no way of knowing what age or level of maturity that spirit exist prior to incarnation and the scriptural texts give zero description for us to interpret from;
2) Jeremiah and his entire life of prophet to the nations IS seen by Yahweh prior to His creating Jeremiah's spirit, Jeremiahs soul, and Jeremiah's body; Yahweh assures Jeremiah that he will succeed as the prophet to nations because Yahweh has ordained it prior to making Jeremiah.
A fair and uncomplicated reading of the text is supporting the second perspective since that is the message Yahweh gives immediately upon placing Jeremiah in time by Yahweh's perspective.
Originally pinged you in #393 and 399, but those posts were so flawed when it registered, I had to do it again in #402.