I KDE5 with task manager set to group programs by name, when you have more than 10 windows of the same name opened, it do not show in the group. You can still access to the windows pressing alt+tab but the scroll bar in the task manager group is gone. Kubuntu 17.04 Plasma 5.9
Could you add a screenshot?
Created attachment 105128 [details] list of first 10 open windows. In the base you still can see/click the 11 window but the rest are gone.
Thanks for the update; changing status.
*** Bug 380054 has been marked as a duplicate of this bug. ***
Git commit 84300b516b799fae94fefd7a9a418e5584d37987 by Eike Hein. Committed on 19/06/2017 at 10:19. Pushed by hein into branch 'Plasma/5.8'. Fix DND onto Task Manager for groups, group dialog scrollbar Summary: With this patch drag-hover activation will work for group children, and moving between different group parents while dragging will correctly refresh the dialog contents. Related: bug 379888 The patch also makes GroupDialog more similar to CompactApplet in desktoppackage/, in particular managing applet status and activa- ting the window explicitly. There is no concrete reason for this, but it seemed like a good idea while debugging the DND issues. Further, while inverting the MouseHandler<>ScrollArea nesting I removed some dodgy geometry-setting code for the inside item, and the ScrollArea viewport now is a single item. This very likely addresses some reports that the scrollbar sometimes wouldn't appear when required. Reviewers: #plasma Subscribers: plasma-devel Tags: #plasma Differential Revision: https://phabricator.kde.org/D6231 M +88 -53 applets/taskmanager/package/contents/ui/GroupDialog.qml https://commits.kde.org/plasma-desktop/84300b516b799fae94fefd7a9a418e5584d37987