Bartender4 is a full ActionBar replacement mod. It provides you with all the features needed to fully customization most aspects of your action and related bars. 

Bartender4 in Midnight: As of version 4.16.5, Midnight support is in preview - it'll be worked on until release, of course.

Major Changes since Dragonflight / 10.0

• Hold-to-cast is not currently available for addons
• Action Bars have been slightly re-arranged in Bartender4 for Dragonflight and beyond
  • Bar 1-8 now reflect Blizzard Bars 1-8 (these are old 1, 3-6, and the 3 new bars)
  • The old bars 7-10 are now called "Class Bar 1-4" (Shapeshifting, Stances, etc)
  • The old bar 2 is now called Bonus Action Bar

 Features

• Support for all Action Bars and all related bars
  • 10 Action Bars (13 in Dragonflight & War Within!)
  • Stance Bar
  • Pet Bar
  • Bag Bar
  • Micro Menu
  • XP/Reputation Bar
• All Bars are fully customizable (Scale, Alpha, Fade-Out settings, ...)
• Very flexible and customizable Show/Hide driver based on Macro Conditions
• Additional Layout and Paging settings for Action Bars
  • Page all bars based on Stance or Modifier
  • Possess Bar support
  • Custom State driver support with Macro Conditions
• Options to hide specific elements of the buttons (Macro Text, HotKey, more could be added on demand)
• StickyFrames support
• Masque/ButtonFacade support!
• Easy Hotkey Binding using KeyBound
• Options to control the hiding of the default blizzard artwork (you might still want that to be displayed..)

FAQ

Q: I cannot move/drag my skills on my bars?
A: Hold Shift to move skills safely. You can also unlock your bars in the Bartender4 options, but using Shift is safer and recommended.

Q: How do i access the Configuration?
A: You can open the configuration with the Slash Commands (/bt or /bartender) or through the Bartender4 LDB plugin.

Q: Where are my keybindings? And how do i bind new keys?
A: Bartender4 buttons should automatically inherit keybindings from the Blizzard bars. For new keybindings, you can use KeyBound to re-bind your keys. You can access KeyBound by its slash command (/kb) or through the button in the BT4 config. Hover a button, press key → voila!

Q: Can I skin the buttons beyond the built-in options?
A: Bartender4 allows skinning through Masque! After installing both Bartender4 and Masque, you can customize the BT4 appearance in the Masque options.

Q: How do i disable the snapping of the bars?
A: Currently, you can temporarily override the snapping by holding down the Shift Key while moving your bars, or uncheck the option in the popup when your bars are unlocked.

Feature Requests/Bug Tracker

Please submit Bugs and/or Feature Requests using the Ticket System on the WoWAce Project page or in the Bartender4 Forum Thread. Please provide as many information as possible, including your client language, the exact version you are running, how to reproduce any errors, and a stack trace, if applicable.

Links

WoWAce Project: Bartender4 on WoWAce
Custom State Header: Info page on WoWAce