I haven't been able to find a way to customize the layout of the encoder toolbar, is this still on the road map?

customizable encoders
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Yes, this is definitely still planned.
If you just need minor tweaks (e.g. moving the "White" colormixing attribute to be immediately next to "Blue"), you can move them in the Attribute Definitions in patch:
- Menu -> Patch -> Attribute Definitions
- Use the syntax: Move x At y