Enable user to create hotspot with formula

I have a user that wants to create a hotspot button in an email and apply a formula to it, however the only option is for simple actions and the ability to change to formula is grayed out. What do I need to enable to allow the user the rights to create this hotspot button?

Subject: Select @formula after you “Add action”

then your user will be able to add code.

To change to formula, the user needs a Designer client

Subject: Thank you for your help and solution