This proposal is complete and already merged into ECMA262 specification. See the specification text here. Thanks for help and feedback on this effort from Brendan Eich, Waldemar Horwat, Jaro Sevcik, ...

When it comes to add empty space between widgets inside a Column or a Row, we have multiple options: We can either add a Padding around these widgets but it's very verbose Or we can add Spacer widgets ...