Classic view/editor plugin + Blocks in post

Hi, i had a look around but couldnt find help. I am in the latest version of WP and using classic view editor/plugin to use the old style. I was trying to add in a block in the new post section to add in a TOC but i couldnt see/find where you add a block on this page (had to convert to new and then back to old).

Is there an easier way or something i can do to simplify this?

 

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