The app framework removal changes at the start of Marlin development included pruning a bunch of mostly unused example images, but that also included the community contributed agl-cluster-demo-qtcompositor image for demoing Qt compositor usage.  There has been a recent inquiry on the mailing list about adding it back for Marlin:

https://lists.automotivelinux.org/g/agl-dev-community/message/9717

Given the somewhat minimal effort required, this seems worthwhile for Marlin 13.0.0.