I've been looking at all the threads on this topic, but nothing quite fits.
On the checkout page, I want customers to see a button to add a donation to our nonprofit, and then they can enter any amount to add as a donation.
This could work as a donation "product" with a variable price but only if I am allowed to add that product to the checkout page.
The "tipping" feature seems to only use percentages.
Are there any solutions to this?