diff --git a/CMakeLists.txt b/CMakeLists.txt
index 058773e494..7be3482738 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -110,6 +110,12 @@ if(KWIN_BUILD_KCMS)
     )
 endif()
 
+if(KWIN_BUILD_TABBOX AND KWIN_BUILD_KCMS)
+    find_package(KF6 ${KF6_MIN_VERSION} REQUIRED COMPONENTS
+        WidgetsAddons
+    )
+endif()
+
 find_package(Threads)
 set_package_properties(Threads PROPERTIES
     PURPOSE "Needed for VirtualTerminal support in KWin Wayland"
diff --git a/src/kcms/options/actions.ui b/src/kcms/options/actions.ui
index 7f84a587b0..0de01f1b36 100644
--- a/src/kcms/options/actions.ui
+++ b/src/kcms/options/actions.ui
@@ -13,6 +13,9 @@
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QGroupBox" name="groupBox_1">
+     <property name="flat">
+      <bool>true</bool>
+     </property>
      <property name="title">
       <string>Inactive Inner Window Actions</string>
      </property>
@@ -180,6 +183,9 @@
    </item>
    <item>
     <widget class="QGroupBox" name="groupBox_2">
+     <property name="flat">
+      <bool>true</bool>
+     </property>
      <property name="title">
       <string>Inner Window, Titlebar and Frame Actions</string>
      </property>
diff --git a/src/kcms/options/main.cpp b/src/kcms/options/main.cpp
index 1fdcf7bbde..fa05782227 100644
--- a/src/kcms/options/main.cpp
+++ b/src/kcms/options/main.cpp
@@ -65,6 +65,7 @@ KWinOptions::KWinOptions(QObject *parent, const KPluginMetaData &data)
     QVBoxLayout *layout = new QVBoxLayout(widget());
     layout->setContentsMargins(0, 0, 0, 0);
     tab = new QTabWidget(widget());
+    tab->setDocumentMode(true);
     layout->addWidget(tab);
 
     const auto connectKCM = [this](KCModule *mod) {
diff --git a/src/kcms/options/mouse.ui b/src/kcms/options/mouse.ui
index 1f55328808..956db6c412 100644
--- a/src/kcms/options/mouse.ui
+++ b/src/kcms/options/mouse.ui
@@ -16,6 +16,9 @@
      <property name="title">
       <string>Titlebar Actions</string>
      </property>
+     <property name="flat">
+      <bool>true</bool>
+     </property>
      <layout class="QFormLayout" name="formLayout_1">
       <property name="formAlignment">
        <set>Qt::AlignHCenter|Qt::AlignTop</set>
@@ -142,6 +145,9 @@
      <property name="title">
       <string>Titlebar and Frame Actions</string>
      </property>
+     <property name="flat">
+      <bool>true</bool>
+     </property>
      <property name="alignment">
       <set>Qt::AlignCenter</set>
      </property>
@@ -223,7 +229,7 @@
         <item row="1" column="1">
          <widget class="QComboBox" name="kcfg_CommandActiveTitlebar1">
           <property name="sizePolicy">
-           <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+           <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
             <horstretch>0</horstretch>
             <verstretch>0</verstretch>
            </sizepolicy>
@@ -338,7 +344,7 @@
         <item row="2" column="1">
          <widget class="QComboBox" name="kcfg_CommandActiveTitlebar2">
           <property name="sizePolicy">
-           <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+           <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
             <horstretch>0</horstretch>
             <verstretch>0</verstretch>
            </sizepolicy>
@@ -453,7 +459,7 @@
         <item row="3" column="1">
          <widget class="QComboBox" name="kcfg_CommandActiveTitlebar3">
           <property name="sizePolicy">
-           <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+           <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
             <horstretch>0</horstretch>
             <verstretch>0</verstretch>
            </sizepolicy>
@@ -588,6 +594,9 @@
      <property name="title">
       <string>Maximize Button Actions</string>
      </property>
+     <property name="flat">
+      <bool>true</bool>
+     </property>
      <layout class="QFormLayout" name="formLayout_2">
       <property name="formAlignment">
        <set>Qt::AlignHCenter|Qt::AlignTop</set>
diff --git a/src/kcms/tabbox/CMakeLists.txt b/src/kcms/tabbox/CMakeLists.txt
index 6d6aa1f759..12b9d056e7 100644
--- a/src/kcms/tabbox/CMakeLists.txt
+++ b/src/kcms/tabbox/CMakeLists.txt
@@ -27,6 +27,7 @@ target_link_libraries(kcm_kwintabbox
     KF6::Package
     KF6::Service
     KF6::XmlGui # For kkeysequencewidget
+    KF6::WidgetsAddons
 )
 if (KWIN_BUILD_X11)
     target_link_libraries(kcm_kwintabbox
diff --git a/src/kcms/tabbox/main.cpp b/src/kcms/tabbox/main.cpp
index e052c6ec83..e6d69ad3aa 100644
--- a/src/kcms/tabbox/main.cpp
+++ b/src/kcms/tabbox/main.cpp
@@ -22,6 +22,7 @@
 #include <QSpacerItem>
 #include <QStandardItemModel>
 #include <QStandardPaths>
+#include <QStyle>
 #include <QTabWidget>
 #include <QVBoxLayout>
 
@@ -29,6 +30,7 @@
 #include <KLocalizedString>
 #include <KNSWidgets/Button>
 #include <KPluginFactory>
+#include <KSeparator>
 #include <KTitleWidget>
 // Plasma
 #include <KPackage/Package>
@@ -55,6 +57,7 @@ KWinTabBoxConfig::KWinTabBoxConfig(QObject *parent, const KPluginMetaData &data)
     , m_data(new KWinTabboxData(this))
 {
     QTabWidget *tabWidget = new QTabWidget(widget());
+    tabWidget->setDocumentMode(true);
     m_primaryTabBoxUi = new KWinTabBoxConfigForm(KWinTabBoxConfigForm::TabboxType::Main,
                                                  m_data->tabBoxConfig(),
                                                  m_data->shortcutConfig(),
@@ -74,17 +77,23 @@ KWinTabBoxConfig::KWinTabBoxConfig(QObject *parent, const KPluginMetaData &data)
     });
 
     QHBoxLayout *buttonBar = new QHBoxLayout();
+    QStyle *style = widget()->style();
+
+    buttonBar->setContentsMargins(style->pixelMetric(QStyle::PM_LayoutLeftMargin), 0, style->pixelMetric(QStyle::PM_LayoutRightMargin), style->pixelMetric(QStyle::PM_LayoutBottomMargin));
     QSpacerItem *buttonBarSpacer = new QSpacerItem(40, 20, QSizePolicy::Expanding, QSizePolicy::Minimum);
     buttonBar->addItem(buttonBarSpacer);
     buttonBar->addWidget(ghnsButton);
 
     QVBoxLayout *layout = new QVBoxLayout(widget());
+    layout->setContentsMargins(0, 0, 0, 0);
     KTitleWidget *infoLabel = new KTitleWidget(tabWidget);
     infoLabel->setText(i18n("Focus policy settings limit the functionality of navigating through windows."),
                        KTitleWidget::InfoMessage);
     infoLabel->setIcon(KTitleWidget::InfoMessage, KTitleWidget::ImageLeft);
     layout->addWidget(infoLabel, 0);
     layout->addWidget(tabWidget, 1);
+    KSeparator *separator = new KSeparator();
+    layout->addWidget(separator);
     layout->addLayout(buttonBar);
     widget()->setLayout(layout);