Blender Selection Border

Simplify UV unwrapping on high poly meshes and dirty geometry in Blender 2.8x

Allow you to select all edges bordering a selection of faces. The edges can be marked as seams, the selection hidden...

The project (and the "documentation") is opensource and can be found on Github here : https://github.com/d1v1d1/Blender-Selection-Border

If you want more tools, options... just ask !