I'm using FM2017 Ditaxml 1.2 to create a new document. I can't figure out how to make certain chapters into appendices. I save the ditamap as Book 2017 w/ FM components... but still can't seem to figure out how to change some chapters to an appendix.
I assume that you're referring to wanting different layout or formatting in the generated appendix components as opposed to chapter components? In the DITA map (bookmap) you can specify that certain top-level topicref-based elements are either chapter elements or appendix elements. But that won't affect the formatting so the FM files that are created from the appendix elements look different than those created from the chapter elements.
Unless things have changed, I think that you'd have to import an alternate template into the generated FM files that you want to be appendix components. In theory, the underlying EDD in the structure application can be set up to determine if it's supposed to be an appendix or chapter and apply the right formatting (and it's possible that the default apps do that .. I'm not sure).
Alternatively, the DITA-FMx plugin (replacement for the default DITA support in FM) is set up to do this automatically, using a concept of "component templates". This allows you to specify different templates for each type of book component. Unfortunately, DITA-FMx is not yet officially available for FM 2017, but it will be soon. If you'd like to play with a beta, please contact me directly.
Is there a way to assign topics as appendices in the ditamap, or do I need to switch my books over to bookmap?