public BigInteger getNextIndex() {
		return layoutModel.getIndexAfter(lastIndex);
	}
Returns the LayoutModel index of the next item that will be returned via {@link #next()}.

@return index of the next Layout item returned, or null if no additional items are present
Ghidra/Framework/Docking/src/main/java/docking/widgets/fieldpanel/LayoutModelIterator.java