map global user p ': buffer-previous<ret>'
map global user n ': buffer-next<ret>'
Although these commands just cycle through the buffers in the order you see them suggested when typing :b<space>. Not something I find very useful. ga takes you to the last buffer you edited and is much more useful IMO.
Kakoune doesn’t support "+ or "* registers by default, and it does not provide a way to add new registers. However, with the RegisterModified hook in the latest release,
you can make any register forward to the system clipboard, including the default (double-quote) register.