Not in SeaMonkey 1.x
Type: comma-separated string
The current set of displayed items on the toolbar. This will be modified when the user customizes the toolbar. The value of this attribute should be a comma-separated list of item IDs from the toolbarpalette or, additionally, any of the following strings: "separator", "spring", "spacer".

this isn't necessary the *current* set, i.e. it might not be equal the value of the currentSet property which is computed from the actual DOM

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 Contributors to this page: Sheppy, ethertank, jswisher, Philip Chee, Marsf, Nickolay, Dria
 Last updated by: Sheppy,