I work at a design agency where UX/UI designers regularly use so-called "smooth corners", or "squircles". It happens more often now that Figma supports these natively.
When handing over the designs to development, they quickly hit a roadblock, because CSS only supports regular rounded corners.
I've made a tiny tool for these exact situations. Now you can add your own corners to your own shapes in vanilla JS, React or Svelte.