For those with fully hidden cables (i.e. passing inside the stem / headset) I would suggest putting the bluetooth junction somewhere in the stem or just behind the bars to make it easier to disconnect the entire handlebar setup in one go.
I put mine just inside the downtube so I can disconnect the bars easily if I want to. Not that I can, given hydro hoses are a bit harder to disconnect.
For those with fully hidden cables (i.e. passing inside the stem / headset) I would suggest putting the bluetooth junction somewhere in the stem or just behind the bars to make it easier to disconnect the entire handlebar setup in one go.