Custom CSS to make one column both fixed + scrollable?

Hi folks, I’ve got a setup that I think can be solved by some custom CSS, although open to alternative solutions. What I’ve built is a block based content management system - IE similar to Mailchimp / Softr etc, with one column showing the content and one column allowing users to edit the selected content

I want the right hand column to remain fixed (IE if a user is editing content further down the page they don’t have to scroll up to see the edit panel), so I’ve used position: fixed. Which works ok.

But the problem is, if there’s too much content in the right hand side, the update button is out of view, and there’s no scrollbar.

I feel like the solution is something like

 position:fixed;
 overflow-y:scroll;

But that’s not working.

Any suggestions? :thinking: