TYPO3: typolink that handles classes in the link field as well as having a custom class in the TypoScript

setup.ts

10 = LOAD_REGISTER
	moreUrl {
		field = linkUrl
		listNum = 0
		listNum.splitChar = 32
	}

	extraClasses {
		field = linkUrl
		listNum = 2
		listNum.splitChar = 32
	}

	link {
		field = linkLabel
		ifEmpty.data = register:linkUrl
		typolink {
			parameter.data = register:linkUrl
			ATagParams.dataWrap = class="{register:extraClasses} btn btn-default"
	}
}

@elmar-hinz, De facto they are evaluated in order. But you can always use 10 for one register, 20 for the other, etc.