The tabs macro takes its tab list from a filter, so here the tabs come out of the data: one per distinct first character, plus an All tab.

Three definitions feed it:

• f.letters collects the distinct first characters
• f.valuesFor selects the groups filed under one character
• f.valuesShown returns everything for All, one character otherwise

This test case carries two payload tiddlers, _TabButton and _TabContent, because the tabs macro transcludes its caption and its panel by tiddler title and cannot take inline wikitext.

Matching is case insensitive, so de Vries and De Vries would share a tab. A character that is not a letter gets its own tab, which is why the sample data produces a 3 tab. Each caption carries the number of groups behind it, so no tab is a dead end.