When attempting to create a tab, the list of available widgets is incomplete, and incorrect - it doesn't show some of the widgets that are currently active, it shows some widgets that aren't active at all, and there are some widgets that aren't shown whatsoever.
Widgets that are shown that shouldn't be: YARPP, Pages: Pages, Calendar:, Archives: Archives, Links, Meta: Meta, Recent Comments: Recent Comments, NextGEN Slideshow
Widgets that aren't shown that should be: Twitter #1: Twitter updates, Most Visited Posts: Popular Posts.
Additionally, the mechanism used - taking active widgets and showing them in a drop-down per tab - seems a little hack-ish. How about doing away with the "Tabbed Widgets" page under "Design" entirely, and instead, using the existing mechanisms, i.e:
1. Like the NextGEN gallery and Twitter plugins, have a form at the bottom of the 'Widgets' page:
How many Tabbed widgets would you like? [...] [Save]
This registers the specified number of widgets for use.
2. Provide per-Tabbed widget options the same way that normal widget options are offered - straight from the Widgets page. One configuration option: Number of tabs
3. For every tab, for every active Tabbed widget (every one added to a sidebar), register a new 'sidebar', that one can select using the dropdown at the top-right of the 'Widgets' page. E.g:
- User adds a tabbed widget
- For the widget configuration, number of tabs is set to 2, and title is set to 'Posts' (title can be hidden, but title must be provided)
- Two sidebars are registered: "Posts Tab 1", and "Posts Tab 2"
- Using the 'Sidebar' selection drop down at the top of the widgets page, user selects 'Posts Tab 1'
- User adds, say, 'Recent posts' widget to the 'Posts Tab 1' sidebar
- User selects 'Posts Tab 2' sidebar
- User adds, for example, 'Popular Posts' widget to 'Posts Tab 2'
This way, the user can have as many widgets as they like inside a tab, and it keeps the whole configuration simple, extensible and relatively compliant.
I might have a go at this some time...