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If you buy a prefilled kit from Shimano this is where the joint is with the olive and nut pre-inserted. See the bottom of the first photo:
https://www.ebay.co.uk/itm/174563306705Not sure why they do this rather than doing the same on the lever directly.
You need to check whether the nut installed on the connector is the same as the nut on back of the lever. If it is you can just whip the extra section out. If not you'll need to cut out the olive and barb and re-terminate it.
I’ve myself some direct mount disc brakes now, but are these junctions on the hydraulic hoses ?