Explanation:
Graphical user interface, text, application, email Description automatically generated

Here are the steps you must follow to add custom controls to a business process flow:
Step 1: Configure custom controls on a related entity.
Step 2: Generate and exporting the business process flow form.
Step 3: Copy custom control configurations to the FormXML for the business process flow.
Step 4: Import customizations into the Microsoft Dataverse environment.
Note:
* Configure custom controls on a related table form.
* Generate and exporting the business process flow form.
* Copy custom control configurations to the business process flow form from the related table form.
* Import the customizations back into Microsoft Dataverse.
Reference:
https://docs.microsoft.com/en-us/power-automate/custom-controls-business-process-flows