At this time, you cannot customize the link to your Checkout Page. One solution many customers have employed is putting this link into a custom link shortener so they can customize the slug of the URL.
A great option for shortening the link is using bitly.com!
To shorten your checkout page link using Bit.ly:
First, Copy the checkout Link
- From your dashboard, select Products then select Forms.
- Choose the offer of the checkout page link you would like to shorten.
- In the offer dashboard, click Get Link and copy the link.
Then go to Bit.ly
- Copy the link in the box titled "Shorten your link"
- then click Shorten.