How to create calculated properties for SEO fields?

Question

1C-Bitrix

I want to write my own description for each city and site,
only how to add a city to the text, I want to replace Moscow with {=region} and https://easypol.ru . on {=site}
Easy installation. CIS delivery. Moscow and Central Federal District: https://easypol.ru .
How can this phrase be customized for each site?
I wanted these computed properties to be available globally

Answer 1

as an option, leave {region} and {site} in the code.
And on the OnEndBufferContent event, replace these codes with the region and site, respectively