You can modify an existing component library and save any changes with additional version notes. However, the updated component library version must be published for use in existing apps that use the component library.
Makers of other apps are notified of updated components being available. The notification appears when makers edit the apps in canvas app studio. They can choose to update the components:

Select Review, and you'll see the option to update the component:

Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/component-library