Right now, the Bevel node works based on the angle between segments (I think?). The bevel can be larger or smaller depending on angle:

Notice that tiny bevel on the right compared to on the left.

To set this up, use the Pen tool to draw a triangle like that above. Then use this button in the top right of the Properties panel to search for "Bevel" and add it. Then drag its distance parameter.

We also want it to work for curved segments, like this, appropriately:

We will then have a follow-on feature for rounding these corners by inserting an arc of a circle in the beveled corners.

We'll also want an option to control the angle at which bevels begin, so that only slight bends don't have to generate bevels.