I think we can save a copy of the flow . Now in the copied flow you can try to remove the first Step which shows a schedule and instead of the same add the button . Try to run the flow and if it works , you can proceed with doing the same step on the original flow .
Please mark my answer as verified if you found it helpful. Please let me know if you have any other questions around the above.
Support Engineer - Customer Engagement- Dynamics CRM/PowerApps/Power Automate