The open carry part had to do with certain types of knives like butterfly and switch blade, they have to be visible
Certainly open carry applies specifically to switch / butterfly, but there seems reason to be cautious about concealed carry of “tactical” type folders:
“Other deadly or dangerous weapon" is limited to instruments whose sole design and purpose is to inflict bodily injury or death. 55 H. 531, 523 P.2d 299 (1974).
A "diver's knife" is neither a "dangerous weapon" nor a "dagger".
"Deadly and dangerous weapon" is one designed primarily as a weapon or diverted from normal use and prepared for combat. 56 H. 374, 537 P.2d 14 (1975).”
I could easily see a Hawaii prosecutor arguing that tactical folders (which are obviously NOT just pocket knives or utility knives) would fall into the class of deadly or dangerous weapons.
I’d be careful here, and make sure you could not be accused of concealment.
The relevant section:
§134-51 Deadly or dangerous weapons; prohibitions; penalty. (a) Any person, not authorized by law, who knowingly carries concealed on the person, or in a bag or other container carried by the person, any dirk, dagger, blackjack, metal knuckles,
or other deadly or dangerous weapon shall be guilty of a misdemeanor; provided that this subsection shall not apply to a billy.
https://www.capitol.hawaii.gov/hrscurrent/Vol03_Ch0121-0200D/HRS0134/HRS_0134-0051.htm