If you turn off Make instance visible in the Launch Excel Action parameter Excel will start as a background process.
When Excel is started as a background process, it is not visible to the user.
Even in this state, it must be terminated by Close Excel Action.
For those who want to learn Power Automate Desktop effectively
The information on this site is now available in an easy-to-read e-book format.
Or Kindle Unlimited (unlimited reading).
You willl discover how to about basic operations.
By the end of this book, you will be equipped with the knowledge you need to use Power Automate Desktop to streamline your workflow.