In MX-21, the new Docklike Taskbar (xfce4-docklike-plugin) replaces the Xfce Window Buttons.
Docklike Taskbar is a lightweight, modern, and minimalist taskbar for Xfce. It provides the same functionality as Xfce Window Buttons, while also providing more advanced “dock” like features.

– Different indicator styles
– Pinnable applications, grouped windows, and desktop actions
– Use Ctrl to reorder your applications or access the settings panel (with right-click)
– Fast application switching : by hovering mouse while button pressed or scrolling
– Window previews (disabled by default)
– Use your Super key to start or switch applications extremely fast

You can access the xfce4-docklike-plugin Properties window several ways:

– Keyboard shortcut Ctrl+right-click on an icon
– Right clicking the empty space between two icons
– MX Tweak – Panel tab
– Xfce4 Panel Preferences application – select the Items tab – double-click Docklike Taskbar (external)

Keyboard shortcuts:

– Ctrl+left-click to begin dragging an item in the dock
– Ctrl+right-click to access Properties, move/remove the plugin
– Shift+click to launch another instance
– Ubuntu Unity style application switching with Super+[1,2,…] (disabled by default)
– Super to switch to the previous application (disabled by default)
– Use the mouse wheel to cycle through open windows

Hidden settings:

Your settings file is located at ~/.config/xfce4/panel/docklike-#.rc
Note: this file is only created after editing any option in the xfce4-docklike-plugin Properties window

– dockSize=<int> sets the minimum width/height (depending on panel orientation) of the dock widget
– previewScale=<double> adjusts the scale factor of preview images (the default value is 0.125)
– previewSleep=<int> adjusts the time, in milliseconds, between new preview images being generated (the default is 250)