Often the answer will be find by asking the question :)
prototype(Vendor.Package:GetMyVar) {
@class = 'Vendor\\Package\\TypoScript\\MyImplementation'
value = ''
}
prototype(Vendor.Package:TSObject) < prototype(TYPO3.Neos:Content) {
templatePath = ...
myVar = Vendor.Package:GetMyVar {
value = ${node.properties.value}
}
}
lg arno