It is easy – just right mouse click on the dendrogram in PATN and select “Save Image…” and then provide a filename, and I suggest stick with the ‘Enhanced meta file’ format as this provides excellent image quality for embedding in applications such as Word.
There is no such thing as ‘saving’ a dendrogram in PATN, except as an image. It is only the PATN project file (in its entirity) that needs to be saved. Each time you clik the dendrogram button on the PATN toolbar, the dendrogram is created afresh. Once a hierarchical classification is run, the dendrogram button should be available (not greyout out).
The only way that the button would not be available would be if a new non-hierarchical classification was run, or that the PATN project file was not saved from the analysis, so when you re-opened the file, no analysis would be available to view or evaluate. Did you click an ‘available’ dendrogram button and nothing at all happened?