Having created a Cell Library containing working Parametric model(s) with Variations, when placing these Models as Cells into a Design the Variations cannot be selected at time of placement.
In order for the Models Parametric Variations to be available when being placed as a cell it has to be placed as a Parametric Cell.
To make the Cell a Parametric Cell:
(Note in the Cell Library Dialog against the Name of the cell its Type if 'Graphic' or 'Point' then the Cell will need to be edited)
Note: If the variables / variations are still not available then see the wiki below as these may be hidden.