Man pages matching name slk_attr in section 3ncurses:

slk_attr.3ncurses.en	debian 10 / ncurses-doc
slk_attr.3ncurses.en	debian 11 / ncurses-doc
slk_attr.3ncurses.en	debian 12 / ncurses-doc
slk_attr.3ncurses.en	debian 13 / ncurses-doc