As LOTRO grows and new UI features are developed, like the new Skirmish Join and Skirmish panels, we have found that we can't just keep adding buttons to the toolbar at the bottom of your screen (or the border of your Radar) to launch the new panels. With this in mind, we set out to create a way for you to launch the new (and existing) features, which will support current needs and allow for future expansion.
Introducing (drum roll please), the new Main Menu!
As you can see in the screenshot (please note that the final version may look slightly different from the screenshots in this diary), we have created a nested structure of menus which will allow you to select the option that you need. You can open a submenu by hovering over the parent item, or clicking on the arrow on the parent item.
The previously-existing Main Menu, having found itself somewhat less than main, is now renamed as the System Menu, and can be invoked from the new Main Menu.
Customize Toolbar Slots:

You can now customize the buttons to perform the functions you want. If you want a button that will open the Kinship panel – go right ahead... Or maybe you want one that will open up the new Mounts panel – not a problem. Any option that you can pick from the new Main Menu is available to select as the action that the buttons will perform.
When the first version of this feature appeared on our Preview Test Server, Isengard, one proposal got a lot of support: Our testers wanted to also be able to remap the buttons on the right hand side, the ones that open the different bags from your inventory. We all thought that was a great idea, and I'm happy to say that we were able to get that added just in time for Book 9.

To access this new feature go to the Options Panel and select “UI Settings”, or click the new Customize Toolbar Slots button just to the left of the Auto-Attack button (highlighted in the screenshot below).
Custom skin developers should be aware that the positioning of the Main Menu is purely dependent on the Main Menu Button. Wherever you move the Main Menu button, the menu will follow.
We hope you enjoy the changes!