I think those wires between the buttons for the display and the display are fixed, I dont think there is a connector, but I am going on the basis of a KT display which I had then sold.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Bafang+extension+cables&_sacat=0
The only other option is to unplug the display, splice the insulation off, cut each wire one by one, and solder an extension wire, remembering to use heatshrink for a nice clean look, or just some neatly placed black electrical tape will work fine as well. Hopefully they use different color wire, that is why I said cut the insulation off first. Then each wire, because maybe a wire has a cap on it with stored energy. Best be safe, not to ruin the electronics right.