Just add a vertical panel to desktop, and set the switch effect to cube. Then switch between pagers, you will see the black area. Reproducible: Always Steps to Reproduce: 1.Add a vertical panel to desktop 2.Set pager switch effect to cube 3.Switch between pagers Actual Results: No black area Expected Results: Black area in top-right part of the screen Debian sid amd64 Framework 5.25 Plasma 5.7.4
Exist in 5.6.x also
*** This bug has been marked as a duplicate of bug 361516 ***