We have created an HTML template for our email and uploaded it through the design tool with a partial template (Standard). However, our template looks good in the preview but is not showing in the custom section while creating a new email and selecting the template.
As same like you when I designed a custom template for my cricket blog and uploaded it. SO I was checking it in the cutom tab. But most of the time it will be shown in the designed template section. Because the custom templated are those which you designed inside the hubspot. SO don't get confused you could used it from the designed section.
Yes, I did upload it as an email instead of page. However, the template I am referring does not have any option like this as it was uploaded as a "Partial Template" which has Standard and Global partial types. I selected Standard Partial.