Hello @eCOMHUB,

Thanks for sharing this question with us.

I noticed you had another thread on the same topic which I replied to here:

I now believe I have a better understanding of your ask, so please allow me to clarify. The fonts that are uploaded in the Brand Library can only be used for custom fonts in your forms, not your email templates. Therefore, you won’t be able to insert custom fonts for your templates directly through the brand library. You’ll find more information on how to insert custom fonts for sign-up forms here, For information on adding custom fonts to your email templates, head to our article on Custom Fonts in Email Templates. 

Additionally, it’s worth pointing out that custom fonts are currently not supported in Klaviyo's new template editor. To use a custom font in your email templates, please use the classic editor. 

I hope that helps clear things up. If you have any additional questions, please leave a reply in the aforementioned thread above. Thanks for being a member of our community.