In Sites view, the side panel (Filters, Timeline, References, etc.) can only be used before selecting a page. Once a page is selected, the panel becomes not clickable/useable. Keeping it functional after selection would allow authors to filter, check references, or review details without deselecting the page.
Improved/Expected Behavior:
Side panel remains interactive after a page is selected
Functions such as Filters, Timeline, and References are fully usable while a page is selected
Applies in Sites view and similar contexts where the side panel is available
Environment Details (AEM version/service pack, any other specifics if applicable):
What you’re expecting is already an existing AEM feature. If it’s not working in your instance, it’s possible that your developer has overridden the out-of-the-box clientlibs, which may be affecting the functionality. I suggest cross-checking this internally.