Smooth multiple selected lines (not faces)

I have a large model terrain that was created from a Topographical TIN mesh. I imported to SU and got someone to go through the entire model and smooth edges between the different grass, asphalt, kerbs etc so these areas could be easily coloured and to take away the jagged look across these surfaces. It took a day as its a large model.

They mistakenly used ‘Shift key’ and eraser tool instead of ‘Ctrl key’ and eraser tool to do this. So instead of smoothing the edges they hid the edge lines. Thus it still has the jagged look and now I would have to colour every individual triangle face to colour the model as surfaces were not merged as they would have been with the smooth tool.

Is there any way to mass convert selected hidden line edges to smoothed edges?
The soften edges tool is no use as I want to retain the edges that divide the model into different materials - grass, asphalt, kerbs etc.

I see that I can soften and smooth multiple selected lines all at once using the “Entity Info” box.

Is anyone aware of a plugin that will allow me to select all the hidden lines at once in the model?

Selection Toys (for the same context selection)

That worked. Excellent, thanks.