Optional port for Node Geometry Editor Frame?

Questions
1

How do you create an optional port for a frame? I want to have rotation port which defaults to 0 if not attached:

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2

you do not wire it and then you select the port itself and flag it as visible in frame

3

I tried that

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and got this error:
10:35:5: Build of NodeGeometry failed: input input from block To radians[GeometryTrigonometryBlock] is not connected and is not optional.

4

Yeah because that node needs a type
But you can add a converter before.