Starting with Firefox version 35.0, the Aurora (“alpha channel”) pre-pre-release version of Firefox has been renamed to Firefox Developer Edition. More importantly for our purposes, by default, it does not use your regular Firefox profile the way Aurora did. When you run it for the first time, it creates a new profile named dev-edition-default.
BookMacster, Synkmark and Markster can access this new profile in the same way that it accesses any other Firefox profile. That is, in the Settings > Clients tab (for BookMacster), and in Preferences > Syncing (for Synkmark), and in File > Import/Export from only…, after running Firefox Developer Edition, you should see at least two profiles, probably default and dev-edition-default.
Actually, you may run your “developer” profile, or any profile for that matter, in the production version of Firefox, and vice versa. I think this is going to be confusing, especially because, when you are in Firefox, the only way to determine your current profile is to click in the menu: Help > Troubleshooting Information, find the Profile Folder section, click the button Show in Finder, and then extract the profile name from the name of the folder they showed you.
By the way: If you have activated Firefox Sync, when BookMacster, Synkmark or Markster export to Firefox in any profile, they will launch an instance of Firefox. They may launch the regular production version of Firefox when syncing to the developer profile, or vice versa. Don’t worry about that.
If you’d like to control your Firefox profiles, as well as manage which version of Firefox to use, Jonathan Griffin’s Profile Manager still works, although it relies on an implementation detail of Firefox that Mozilla could break at any time. When trying to understand Profile Manager, remember that it’s dealing with two dimensions: the profile and the instance of Firefox to run (typically production, beta, or Developer Edition), and that both variables have their own default setting and currently-active settings. To rename a profile in Profile Manager, perform a secondary click on it. Rename is in the contextual menu which will appear.
Long ago I filed a bug with Mozilla asking that they make the current profile readily apparent, the way Google did when Chrome introduced multiple profiles. So far, the wonky Troubleshooting Information explained above is all we’ve gotten. Maybe if Mozilla gets a ton of support requests from people using Developer Edition who have got their profiles confused, they’ll finally realize the wisdom of making the current profile more apparent..