Inserting Aria-Landmarks Into Blocks

Hello everyone!

This is my first time posting to this forum.

I am trying to add landmarks to a new template I made on my website.

Here is how I use to do it.

1. Create the template part, for example, the general area where the content is posted.
2. Insert the <main> landmark with the custom HTML block, and then insert the </main> in the custom HTML block at the end of my content.

The problem is that when I edit the template part, I get a warning that says I can recover the block or something like that.

Is there another way to create the aria landmarks with the post title in the same block or something?

Thank you.

The page I need help with: [log in to see the link]