The Code should be
Then it would show up as Test-Product Templates in Stlye Manager.

Don't use the last underscore.

Thanks!

In review, just to make sure I have the process down:

1) Enable debug mode.
2) Enable plugin system.
3) Add your product using the manager.
4) Create custom setting groups.
5) Create custom settings.
6) Create custom phrasegroups.
- A) SELECT MAX(phrasetypeid) + 1 AS newid FROM phrasetype WHERE phrasetypeid < 1000
- B) INSERT INTO phrasetype (phrasetypeid, ...) VALUES ('$newid', ...)
- C) ALTER TABLE language ADD phrasegroup_whatever MEDIUMTEXT NOT NULL
- D) Rebuild languages
7) Create custom phrases.
8) Create custom templates beginning with a unique prefix in lowercase, such as poduct_name.
9) Tweak existing templates if needed.
10) Create the $only['product_name'] = 'Product Name'; plugin for your product using the template_groups hook.
11) Create any other hooks plugins your product needs.
12) Write new files.
13) Hack old files if needed.
14) Export your product to xml.
15) Package it with a small script to install the tables and explain manual tweaking of existing templates and files.

Done. Right?

Installation of new tables can be handled from the Product Manager, no need for installation scripts.

@Albus
That's it - yes. But as Marco already pointed out, creating/altering tables can (and should be) handeled with product install/uninstall codes.
Also there is a function to create custom phrasetypes: add_phrase_type() in adminfunctions_language.php
Just the GUI is missing :(
I pointed this out @ .com, but the Devs don't seem to see a need for it.
For my needs, I ported this Hack - makes it easy to handle Phrasegroups :)
I've contacted the author if he plans to release it, but did not get a reply so far.

Hm, so technically I can create it all online and use the install/uninstall code boxes to make the call to add_phrase_type() and handle the table work? I see there's a version number field there too. This raises two questions.

1) How does the version number affect rollbacks to a previous version, should the user wish to do so? I realize that you'd have two install codes and two uninstall codes.

2) How does this affect the order the product is installed in? In other words, what's the order of things? Install code, settings, phrases, templates, etc...

Sorry for the all the questions, but I want to make absolutely sure I know what I'm doing.

One more thing...is the 'vb' product name prefix still in effect? If so, how do things like vbadvanced name their products? I ask because I recently registered a development domain that starts with vb and would like my products to bear that prefix.

Once you've created a product XML you don't have to take care of phrase and phrasetype stuff, vBulletin will handle that itself.
I was only babbling about initially creating the phrasgroup on your developement machine.

A rollback is not possible (yet?), the User can only uninstall.

Installation order is
- Install-Code
- Templates
- Plugins
- Phrases
- Settings

On uninstall, uninstall codes will be called in reversed order (og. newest version first).

Prefix vb is reserved for Jelsoft use, yes.

Ooh, that's nice. I think that wraps it up. One of us ought to compile all the instructions, comments and questions here so far into a downloadable document. Thanks!

Where is writing the actual XML for a product covered?

Take a look at some other products... most of the time you can generate them (export product), but sometimes you may have to go and edit the XML yourself.