Selecting Facet Edges

In addition to selecting facets, you can select facet edges and edge loops.

Use Shift+Double-click on sharp (>60°) internal edges that form an isoline (edges that are nearly continuously tangent to each other as the line propagates).

The selection will be the best polyline found and not necessarily a complete loop. As you can see in the image below, the selection stops at the cylinder because adjacent edges are not within the tolerance (<10°) to be considered tangent.

Use Ctrl+Shift+Double-click on sharp edges to select multiple mesh edge isolines.

Double-click the Boundary mesh edges to highlight and select the boundary edges