Hide the donation product from your "Default collection"
On Shopify your Default collection is usually access with the url /collections/all. Follow these steps to create a "Default collection" to override the existing /collections/all url in your store and add a rule to exclude the Donation product.
From your Shopify admin navigate to Products > Collections and select the utton [Create collection].
Set the title to "All".
Under Collection type choose "Automated".
Next add a condition with the parameters - Product title - is equal to - "Donation"
Click Save in the top right.
Now when customers navigate to /collections/all in your store the Donation product will no longer be visible.
Hide the donation product from search and search engines
It is unlikely that your customers will search for the Donation product. However if you would like to hide it from search and search engines follow these steps.
Create a custom field
From your Shopify admin go to Settings > Custom data > Products
Next add the name of the field and set the Namespace and key to - seo.hidden
Next go to Products, search for the Donation product and open it.
Navigate to the bottom of the Donation product page to where you see the field you created for hiding products.
Set the value of this field to 1.
Click [Save] in the top right of the screen.