When users or sites in Matomo have very large reports or for dashboards that have a lot of widgets, it can often times mean that users need to constantly scroll up to the top of the page any time they want to select a different date range, a different segment or even website.
Having the option to be able to 'freeze' the selectors to the top of the page so it doesn't get hidden when scrolling would be great.
This would also have the added benefit that users who are taking screenshots of reports to be shared with teams or via external methods are able to scroll to the part of the report they need to reference and have all of that information directly visible in the screenshot. It would also benefit users to be able to quickly confirm that they're viewing the correct reports without needing to change where they are on the page.
I think it would be very useful feature for accessibility as well (Especially for those with impaired mobility where navigating up and down the page is more challenging)