I tried to use the MnzkSyncScroll plugin having EE 7.0b6 installed, and it did not work: the button is shown as pressed, but only one window is scrolled.
PS: Added later: I’ve just found that in some cases the plugin works but very unstable – the other EE window is sometimes scrolled, sometimes not, sometimes it is scrolled but the number of lines scrolled is different than I scrolled in the first window…