Reserving inventory on a draft order in Shopify

Learn to reserve inventory on draft orders with instructions and screenshots with Rich Commerce's "Reserving Inventory on a Draft Order in Shopify".
For exchanges, Rich Returns allows store owners to either create a (real) order in Shopify or a draft order. The draft order option does not reserve inventory for the new item until it is converted to a real order in Shopify.
The option in Shopify's dashboard to Reserve items will NOT reserve inventory according to merchant reports in the Shopify forums, see e.g.
Shopify does not offer functionality of reserving items for draft orders to developers, yet. So the only option Shopify allows at the moment is to either create a real order (deducts inventory) or a draft order (does not deduct inventory).