Round corners only become visible if the component has for example a background or a border.
To edit the round corners of any component:
- Right-click on the component to access its context menu
- Open its general Style setting
- Find the Round corners setting
- Optionally, disable Apply to all corners for controlling each corner separately
- Use the input field or the range input to change the border width. The input field allows you to set values beyond the limit of the range.