After latest update, the settings of the folder pane are no longer preserved; all values of visible columns are always set. If I uncheck these boxes it is only valid for thge current and next session. Then, all boxes are checked and all columns are visible again. It seems that is belong to a setting in kmail2rc: if I delete the value "HeaderState" in section "[CollectionFolderView]" (or even the whole section), the columns are not visible on the next start, but at the overnext start shows again all unwanted columns (unread, summary and size).
qt-5.10.1 ?
Yes: Qt 5.10.1 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 7.3.0) on "xcb" Interesting behaviour: if I widen the columns until none of the unwanted columns are visible and I unchecked the three boxes, then on next (and overnext) start the status kept unchecked. I can check and uncheck every box, and they keep their state. Once I narrow the foldername column until the horizontal scrollbar disappears, it's still OK, if I check one box again, like "unread", then on next start all three boxes are checked again and the columns are visible. For a first workaround it should be a solution for me to widen the filename column until the other columns are no longer visible, then it seems to keep the state after switch off the unwanted columns.
it's a regression in qt5.10.1... We need to wait that qt fix it.
*** Bug 391419 has been marked as a duplicate of this bug. ***