diff --git a/src/ZenCompactMode.mjs b/src/ZenCompactMode.mjs
index 767c64e..97fe7d1 100644
--- a/src/ZenCompactMode.mjs
+++ b/src/ZenCompactMode.mjs
@@ -1,5 +1,5 @@
 var gZenCompactModeManager = {
-  _flashSidebarTimeout: null,
+  _flashTimeouts: {},
 
   init() {
     Services.prefs.addObserver('zen.view.compact', this._updateEvent.bind(this));
@@ -8,6 +8,7 @@ var gZenCompactModeManager = {
     gZenUIManager.addPopupTrackingAttribute(this.sidebar);
     gZenUIManager.addPopupTrackingAttribute(document.getElementById('zen-appcontent-navbar-container'));
 
+    Services.prefs.addObserver('zen.tabs.vertical.right-side', this._updateSidebarIsOnRight.bind(this));
     this.addMouseActions();
   },
 
@@ -19,6 +20,13 @@ var gZenCompactModeManager = {
     Services.prefs.setBoolPref('zen.view.compact', value);
   },
 
+  get sidebarIsOnRight() {
+    if (this._sidebarIsOnRight) {
+      return this._sidebarIsOnRight;
+    }
+    return Services.prefs.getBoolPref('zen.tabs.vertical.right-side');
+  },
+
   get sidebar() {
     if (!this._sidebar) {
       this._sidebar= document.getElementById('navigator-toolbox');
@@ -38,6 +46,10 @@ var gZenCompactModeManager = {
     this._flashSidebarDuration = Services.prefs.getIntPref('zen.view.compact.toolbar-flash-popup.duration');
   },
 
+  _updateSidebarIsOnRight() {
+    this._sidebarIsOnRight = Services.prefs.getBoolPref('zen.tabs.vertical.right-side');
+  },
+
   toggleSidebar() {
     this.sidebar.toggleAttribute('zen-user-show');
   },
@@ -58,47 +70,100 @@ var gZenCompactModeManager = {
 
   get hoverableElements() {
     return [
-      this.sidebar,
-      document.getElementById('zen-appcontent-navbar-container'),
+      {
+        element: this.sidebar,
+        getScreenEdge: () => this.sidebarIsOnRight ? "right" : "left",
+      },
+      {
+        element: document.getElementById('zen-appcontent-navbar-container'),
+        getScreenEdge: () =>  "top",
+      }
     ];
   },
 
-  flashSidebar(element = null, duration = null) {
-    if (!element) {
-      element = this.sidebar;
-    }
-    if (!duration) {
-      duration = this.flashSidebarDuration;
-    }
+  flashSidebar(duration = this.flashSidebarDuration) {
     let tabPanels = document.getElementById('tabbrowser-tabpanels');
-    if (element.matches(':hover') || tabPanels.matches("[zen-split-view='true']")) {
+    if (!tabPanels.matches("[zen-split-view='true']")) {
+      this.flashElement(this.sidebar, duration, this.sidebar.id);
+    }
+  },
+
+  flashElement(element, duration, id, attrName = 'flash-popup') {
+    if (element.matches(':hover')) {
       return;
     }
-    if (this._flashSidebarTimeout) {
-      clearTimeout(this._flashSidebarTimeout);
+    if (this._flashTimeouts[id]) {
+      clearTimeout(this._flashTimeouts[id]);
     } else {
-      window.requestAnimationFrame(() => element.setAttribute('flash-popup', ''));
+      requestAnimationFrame(() => element.setAttribute(attrName, ''));
     }
-    this._flashSidebarTimeout = setTimeout(() => {
+    this._flashTimeouts[id] = setTimeout(() => {
       window.requestAnimationFrame(() => {
-        element.removeAttribute('flash-popup');
-        this._flashSidebarTimeout = null;
+        element.removeAttribute(attrName);
+        this._flashTimeouts[id] = null;
       });
     }, duration);
   },
 
+  clearFlashTimeout(id) {
+    clearTimeout(this._flashTimeouts[id]);
+    this._flashTimeouts[id] = null;
+  },
+
   addMouseActions() {
     for (let i = 0; i < this.hoverableElements.length; i++) {
-      this.hoverableElements[i].addEventListener('mouseenter', (event) => {
-        let target = this.hoverableElements[i];
+      const target = this.hoverableElements[i].element;
+      target.addEventListener('mouseenter', (event) => {
         target.setAttribute('zen-user-hover', 'true');
       });
 
-      this.hoverableElements[i].addEventListener('mouseleave', (event) => {
-        let target = this.hoverableElements[i];
-        this.flashSidebar(target, this.hideAfterHoverDuration);
-      });
+      if (this.hoverableElements[i].keepHoverDuration) {
+        target.addEventListener('mouseleave', (event) => {
+          this.flashSidebar(target, keepHoverDuration, target.id, 'hover-timeout');
+        });
+      }
     }
+
+    document.body.addEventListener('mouseleave', (event) => {
+      for (let i = 0; i < this.hoverableElements.length; i++) {
+        const target = this.hoverableElements[i].element;
+        const edge = this.hoverableElements[i].getScreenEdge();
+        if (!edge) return;
+        const orient = (edge === "left" || edge === "right" ? "vertical" : "horizontal");
+        if (
+          this._getNearestEdge(document.body, event.pageX, event.pageY) === edge
+          && this._positionIsAligned(orient, target, event.pageX, event.pageY, 7)
+        ) {
+          this.flashElement(target, this.hideAfterHoverDuration, target.id);
+
+          document.addEventListener('mousemove', () => {
+            target.removeAttribute('flash-popup');
+            this.clearFlashTimeout(target.id);
+          }, {once: true});
+        }
+      }
+    });
+  },
+
+  _getNearestEdge(element, posX, posY) {
+    const targetBox = element.getBoundingClientRect();
+    let smallestDistance = Infinity;
+    let closestEdge = "";
+    for (let edge of ["top", "bottom", "left", "right"]) {
+      const onXAxis = edge === "left" || edge === "right";
+      const distance = Math.abs( (onXAxis ? posX : posY) - targetBox[edge]);
+      if (smallestDistance > distance) {
+        smallestDistance = distance;
+        closestEdge = edge;
+      }
+    }
+    return closestEdge;
+  },
+
+  _positionIsAligned(axis = "x", element, x, y, error = 0) {
+    const bBox = element.getBoundingClientRect();
+    if (axis === "x") return bBox.top - error < y && y < bBox.bottom + error;
+    else return bBox.left - error < x && x < bBox.right + error;
   },
 
   toggleToolbar() {