Where can developers find the "Corner smoothing" value?

This is not something that developers can use. This feature is only made for making icons so it doesn’t make sense to put it in the inspect panel, since developers have no way to implement it in apps/websites. The only way to make it work in the product interface would be vector SVG or rasterized assets (png).

Although it was fun to learn about squircles, having this implemented into a product design tool feels like a trap. A disappointing dead end to this learning exercise. It would make more sense to move this functionality into the edit-vector-mode if this is only supposed to be used for vectors and icons.

hard agree, very sad that I have to ignore this right after finding it.

you can develop it by tracing a path

Developers can apply this to rounded corners in SwiftUI using the RoundedCornerStyle.continuous property. Presumably, this property specifies a smoothing value similar to Figma’s iOS suggestion of 60% in the Corner Smoothing UI. However, even in the new Dev Mode, the Code panel still only exports a standard corner radius property.

Considering the monstrous amount of work completed by Daniel Furse to implement the corner smoothing feature in Figma, I think this simple line of code should be added to the SwiftUI code export (maybe for all layers that have a corner smoothing value greater than 0?).

RoundedCornerStyle.continuous

Great stuff! In this case yes, this definitely should be added.