I have tried both defining the path by setting the start and end points as nodes, and also by defining an edge type path and selecting the edges themselves. I also used the "snap to mesh nodes" context option on the paths.
In either case, I get the same problem - I do not get "path" as an option as a scoping method. If I right-click on my solution results objects (like thermal strain) and click "convert to path result", it changes the scoping method option to "path" and creates a new path, presumably corresponding to the existing geometry selection. "Path" is highlighted yellow, and clicking on the scoping method field does not offer path as an option. I am able to choose any path, but it does not solve and does not produce an error message. I will try this again in the 2022 version and see if the issue persists.
Is there an option to plot across the length of an edge defined by a named selection? The only chart option I see is over time and while picking an edge will show the color localized to a line in the viewport, it is not very useful for extracting actual data.