Fiducial markups not showing in 4.11.0

We always maintain backward compatibility with at least the previous major version (and as much as possible, with earlier versions, too).

The problem you encountered is due to that Slicer-4.10 did not take into account slice visibility attribute for markup nodes and Slicer-4.11 does (and by default slice visibility was turned off for markups).

As a workaround, you can right-click on eye icon of the markups node in Data module and check “2D visibility”, I’ve also submitted a fix that enables 2D visibility for markups by default when an old scene is loaded (it will be available in Slicer Preview Releases downloaded tomorrow or later).