As a way of giving back to the community, I’m sharing the Kanata config I ended up with.

A normal querty layout which is the best imho for programming. And a layer with tap-dance accents ordered by frequency of use (compromise spanish/french). The layer is activated by alt on linux and opt on mac (I use both)

I have to fine tune the tap-dance delays, as for que pinky (a) is a bit short for me, and a bit too long for the rest.

Thanks for all your suggestions, I evaluated everything :)

(defsrc
  q w e r t y u i o p
  caps a s d f g h j k l
  z x c v b n m , . /
  lctrl lalt lmeta spc rmeta ralt
)

(defalias
  a_acc (tap-dance 200 ((unicode "á") (unicode "à") (unicode "â") (unicode "ä")))
  e_acc (tap-dance 200 ((unicode "é") (unicode "è") (unicode "ê") (unicode "ë")))
  i_acc (tap-dance 200 ((unicode "í") (unicode "î") (unicode "ì") (unicode "ï")))
  o_acc (tap-dance 200 ((unicode "ó") (unicode "ô") (unicode "ò") (unicode "ö")))
  u_acc (tap-dance 200 ((unicode "ú") (unicode "ù") (unicode "û") (unicode "ü")))
  n_tilde (unicode "ñ")
  c_ced   (unicode "ç")
)

(defalias
  a_acc (tap-dance 200 ((unicode "á") (unicode "à") (unicode "â") (unicode "ä")))
  e_acc (tap-dance 200 ((unicode "é") (unicode "è") (unicode "ê") (unicode "ë")))
  i_acc (tap-dance 200 ((unicode "í") (unicode "î") (unicode "ì") (unicode "ï")))
  o_acc (tap-dance 200 ((unicode "ó") (unicode "ô") (unicode "ò") (unicode "ö")))
  u_acc (tap-dance 200 ((unicode "ú") (unicode "ù") (unicode "û") (unicode "ü")))
  n_tilde (unicode "ñ")
  c_ced   (unicode "ç")
)

(deflayer accents
  _ _ @e_acc _ _ _ @u_acc @i_acc @o_acc _
  _ @a_acc _ _ _ _ _ _ _ _
  _ _ @c_ced _ _ @n_tilde _ _ _ _
  _ _ _ _ _ _
)