dropdown menu for tabs that cannot be displayed (#7918)

* The visibility threshold is 75%
* Used in remote, file transfer, port forward and cm

Signed-off-by: 21pages <pages21@163.com>

flutter/lib/desktop/pages/file_manager_tab_page.dart

@@ -99,7 +99,7 @@ class _FileManagerTabPageState extends State<FileManagerTabPage> {
           body: DesktopTab(
             controller: tabController,
             onWindowCloseButton: handleWindowCloseButton,
-            tail: const AddButton().paddingOnly(left: 10),
+            tail: const AddButton(),
             labelGetter: DesktopTab.tablabelGetter,
           )),
     );