Because I've been using Marked.app mainly for Leanpub writing, I spent some time switching my laptop over so it would use the kramdown library for rendering (as Leanpub does) instead of the standard MultiMarkdown library.

There are a couple of issues I won't go into here regarding tricks in installation and path variables when getting this set up. The main problem/suggestion I'd like to bring up is the lack of feedback from Marked.app itself when a custom processor has been selected, but for whatever reason isn't found or fails for some other reason.

As far as I can tell, if a custom processor can't be found, the default MultiMarkdown processor is used instead. But this happens silently, in the sense that no visible warnings or alerts are raised in the app. In some situations a console message is generated, but it seems to me that console messages of the form command not found should be important enough to capture and report immediately to the user.

I don't care if a warning is added to my rendered document, or a message box is opened, or a red alert appears in the Preference pane when I enter an invalid path into the Custom Processor field. But something ought to let me know as soon as possible that what I see isn't what I expect to see.