I noticed another similar topic where a user needed to untrim in Creo Direct Modeling. I tried some of the ideas but couldn't seem to make anything work.
Perhaps this works different in Creo Parametric.
I have tried Edit Definition to the imported IGES. I clicked the Edit Data icon and then clicked on an edge which I deleted. Unfortunately this doesn't untrim the surface in which the edge is attached to as shown in the video.
Any ideas how this would be done?