Some category updates

I made it easier to select your category in the New Topic editor.

You can now type in here:

You'll notice that subcategories are also shown.

Also per a request from @ronshere, I've moved most of the hearing aid software requests into this subcategory ("Fitting Software Requests") of DIY. Please use that going forward and continue flagging posts that aren't in the right category, for our review.
Thanks all!