If you didn't already, consider taking look at the details/summary elements (https://caniuse.com/#search=summary https://caniuse.com/#search=summary) which prov

If you didn't already, consider taking look at the details/summary elements (https://caniuse.com/#search=summary https://caniuse.com/#search=summary) which provide a non-JS method for collapse-by-default and as of late have quite good evergreen support. They're fairly versatile, I've even used them recently for JS-free context menus. The only gotcha (the 80% implementation part) is in consistently overriding their default styles on all platforms.