Worked a bit more on split view groups

src/browser/base/content/zen-styles/zen-folders.css

@@ -37,6 +37,12 @@ tab-group[split-view-group] {
   & .tab-close-button {
     display: none !important;
   }
+
+  @media (prefers-reduced-motion: no-preference) {
+    #tabbrowser-tabs[movingtab] & {
+      transition: var(--tab-dragover-transition);
+    }
+  }
 }
 
 tab-group[split-view-group] .tabbrowser-tab {

src/browser/base/zen-components/ZenFolders.mjs

@@ -19,6 +19,12 @@
     #onTabUngrouped(event) {}
 
     #onTabGroupRemoved(event) {}
+
+    expandGroupTabs(group) {
+      for (const tab of group.tabs) {
+        gBrowser.ungroupTab(tab);
+      }
+    }
   }
 
   window.gZenFolders = new ZenFolders();

src/browser/base/zen-components/ZenViewSplitter.mjs

@@ -565,6 +565,8 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
    * @param {number} groupIndex - The index of the group to remove.
    */
   removeGroup(groupIndex) {
+    const group = this._data[groupIndex];
+    gZenFolders.expandGroupTabs(group);
     if (this.currentView === groupIndex) {
       this.deactivateCurrentSplitView();
     }
@@ -721,7 +723,7 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
       } else {
         // Add any tabs that are not already in the group
         for (const tab of tabs) {
-          if (!group.tabs.includes(tab)) {
+          if (!group.tabs.includes(tab) && tab.pinned === group.pinned) { 
             group.tabs.push(tab);
             this.addTabToSplit(tab, group.layoutTree);
           }