Dropdown menu in navigation symbol to show or hide depending on current page


I am trying to create a sidebar symbol that has a number of dropdown menus inside. Ideally, I’d like each dropdown menu to be expanded by default, and only on the relevant page.

For example, if you’re on the Colour page, you will have access to all the section links for Primary, Greys etc, but won’t be able to access any other sub-menus nested under Tone of voice for example.

If you want to see the section links for a particular page, you will have to navigate to that page where the submenu will be shown by default, and all other sub-menus are hidden.

Does anyone know the best way to achieve this?

Thanks in advance.

Here is my site Read-Only: LINK