Conditional Palettes

Yes.
This may not be exactly what you had in mind, but it is easy to create and maintain:

  1. Greate one Macro Group for Each app with the macros you want on the pallet for that app.
    • Add a Macro (the same macro) that Shows Macros from #2.
  2. Create on Global Macro Group (I call it "Global Palette") for the global macros you want included in each app palette

So it looks like this:

Palette for A Specific App (Outlook in this case)

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Press "G" to show the Global Macros

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Here's the setup:

App Palette

Global Palette

Adapt as need to meet your specific needs/preferences.