Export the Flow:

Extract the zip file and navigate to /extractedfolder/Microsoft.Flow/flows/GUID/ and open definition.json

When I used Notepad++ with the JSTool plugin it sorted the code differently and would not work so I used Visual Studio Code and Shift+Alt+F sorted the JSON correctly.
https://code.visualstudio.com/Download#

Search for one of your inputs to find the section where the JSON is located

In this example I want Assigned To BEFORE Assigned By in my instant flow

So I highlighted from the , to the } and cut the code out (Ctrl+X)

Then I clicked between the }, on the line above email_1 and pasted (Ctlr+V) the code back in and as you can see email (Assigned To) is now above email_1 (Assigned By)

Now this part was a little tricky and messed me up a bit. Don’t simply re-zip the folder back up. When I did that the file would not import.

Instead open a new explorer window and double click the original zip file you downloaded and navigate to Microsoft.Flow/flows/GUID/

Drag the new definition.json file you edited into the zip file location and overwrite the old one

Next go to Power Automate and click My Flows on the left and click Import

Click Upload and select the zip file that you updated the definition.json file with

Click the wrench on the far right for the Name row with resource type flow

Make sure Update is selected then find the flow you want to update and click the item and it will put a check mark next to it. Then click Save

Follow similar steps for the SharePoint Connection I won’t cover that part then click Import

The order did not immediately change in my flow when I clicked edit on the item however when running the instant flow it was in the correct order

After a couple minutes it showed up in the correct order when editing the flow

Hope this helps someone!!

Reference: https://powerusers.microsoft.com/t5/Power-Automate-Ideas/Order-Flow-buttons-inputs/idc-p/792558/highlight/true