So far tabbed dialogs were designed with a GtkBox including image and label as tab widget. This has some flaws and was replaced by ui-less tabs, ie. created per code. The patch 05919359717b8b7b2fff6ad73088d34ee397e297 works fine yet might have some follow-up issues. Namely the previous tab configuration crashes with the option to show tabs horizontally (bug 167108) and in some cases the "Tab Page ID '' not known" which leads to empty tabs. Might be unrelated as the internal tab string is being harmonized as well (for example "labelTP_PARA_STD" -> "indents").
*** Bug 167451 has been marked as a duplicate of this bug. ***