Taskbar Shuffle is a simple, small, free utility that lets you drag and drop your Windows taskbar buttons to rearrange them.
Here’s a full feature list:

• Full 32-bit and 64-bit support
• Reorder your taskbar buttons by dragging and dropping them
• Reorder your tray icons in the same way
• Reorder tasks in a grouped button's popup menu in the same way
• Middle-click to close programs on your taskbar
• Works with UltraMon (version 3+ only) taskbars
• Tweak taskbar button grouping

Portable Taskbar Shuffle - 64bit software

• Taskbar Shuffle
• Latest version: 2.5
• Release date: 2009-04-27
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