Hi @Barnard, Monique ,
Welcome to Q&A forum!
If you want to add button in command bar only, you try to use SPFx ListView command set. This need you have development experience.
And there is one way using JSON formatting to show the button in list view which will run power automate flow. But, the button will be shown against each list/library item & not in command bar.
For you reference: Create a button to launch a Flow
Good day!
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