Tested versions

• Reproducible in 4.6.dev6
• Not reproducible in 4.5

System information

Windows 11, Godot 4.6.dev6

Issue description

In 4.6 template there's no background on the node tree in the 'Create New Node' window making it hard to tell where the tree ends and the split panel begins:

Here is 4.5:

This is a usability issue as that split panel lets you resize it to make reading node descriptions easier, so it's very helpful for the user to know exactly where it is:

Steps to reproduce

• Click the 'add new node' button on any scene.

Minimal reproduction project (MRP)

N/A