Is there a specified procedure to change a hierarchical design to flat?
I wouldn't think there is. But you can allways Cut or Copy the content of a block, and Paste it to any other page within your project (or any other project). But be aware of this, especially when you use blocks multiple times: Within the block every net has a name, that can be copied together with the rest. You can force Designer to assign new net names when you Cut or Copy parts of your schematics (hit your keyboard's "Space bar" and type "uon", or go to Setup --> Setting --> Advanced and deselect "Unique Names on Copy"). If you miss this, you will get some short circuits.
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