You can use the IIS settings for that. It is first necessary to install the URL Rewrite module in IIS and then create a rule for adding or removing the trailing slash of site URLs.
I am attaching a screenshot that shows you the installed URL Rewrite in IIS as well as the option for enabling the trailing slash rewrite rule in your website.
We have a small issue
related to enabling both lower case letters and trailing slash that we have included in our PITS system. You can keep up to date with its resolution at this address. I have raised the business priority of this ticket so that we can resolve it as soon as possible as it is important for SEO purposes.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items