Preserve previous tab when navigating to and from contact page
The contact page is structured around a series of tabs: Summary, Contributions, Membership etc. There are often times when you click through from a contact to a related entity (say a related contact from the relationships tab). It would be nice if using the browser's back button returned you to the tab you were previously looking at rather than returning to the summary tab each time.
This is a bigger issue for users with the "Enable Popup Forms" option unticked, but all users are affected by this.
This shouldn't be a massive technical change, but I do think this is one of those little annoyances, where fixing should improve the overall usability of the CRM for those who need to use it on a daily basis.
Implementation details
It is already possible to link to a specific tab with the selectedChild query parameter. I propose that whenever the active tab is changed, the replaceState API is used to amend the selectedChild parameter in the URL.