Regardless of where anyone else tied into the 12v battery, you have four possible choices (as you have marked on your picture):
1 - The one with the yellow arrow is the best choice, IMO, due to ....... it's protected by a 200amp fusible link. (you have it marked with a purple X) and serves no function for the LC's systems, other than a convenient place to attach to the 12v battery
2 - The one you have marked with a green circle would be my 2nd choice but adds to the amount of stuff hanging off the battery's POS post and would need to be removed/loosened if a battery change out was required in the future.
3 - The green circle with the purple X through it, is essentially the same as the POS battery post.
4 - The 2nd one marked with a purple X, while it would work, it is connected to the main 350 amp fusible link that's the power source for the rest of the LC's computers and if it blows your LC just became a brick.
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