See related kde bug [1], the proposed patch resolve the issue. [1] https://bugs.kde.org/show_bug.cgi?id=393912 Reproducible: Always
Same bug, last comment, there is report of a regression with the patch. I'm not sure we should apply this until this is cleared, but maybe you can try and reproduce the issue.
I already applied the patch and I haven't encountered the regression, I can move window on any activity without problem (with right click on window title bar and then Activities -> ...)
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=c238ad1a982cc26cc3a8aef14a8ee6d2b2adfe4b commit c238ad1a982cc26cc3a8aef14a8ee6d2b2adfe4b Author: Andreas Sturmlechner <asturm@gentoo.org> AuthorDate: 2018-09-04 12:13:22 +0000 Commit: Andreas Sturmlechner <asturm@gentoo.org> CommitDate: 2018-09-04 12:25:46 +0000 kde-plasma/plasma-desktop: Fix activity switcher autohide Closes: https://bugs.gentoo.org/663032 Package-Manager: Portage-2.3.48, Repoman-2.3.10 .../plasma-desktop-5.13.5-activityswitcher.patch | 62 ++++++++++++++++++++++ .../plasma-desktop/plasma-desktop-5.13.5.ebuild | 2 + 2 files changed, 64 insertions(+)