Youdaman

Ever want to make an element stick to a page? Well now you can! 
Just install this WordPress plugin and your wish will be granted!

Sticky Element

followalter

This plugin makes the right sidebar on post.php pages (where you edit a post) stick to the top of the screen when you scroll, so all functions of the sidebar stay within reach. It’s works with the classic version of the editor.
If the total height of the sidebar is larger than the window height, the sidebar sticks to the bottom instead, so the whole sidebar can be made visible through scroll.
On top of this, when you publish or update a page, the plugin will make the page scroll down to the previous scroll position.
This saves users from both having to scroll up (because of the stickyness) and having to scroll down again (using the previous scroll position) every time they update a post!

Admin Sticky Sidebar

This plugin makes the right sidebar on post.php pages (where you edit a post) stick to the top of the screen when you scroll, so all functions of the  …

Sticky Element vs Admin Sticky Sidebar