We give the construction of weighted Lagrangian Grassmannians wLGr(3,6) and weighted partial A3 flag variety wFL1,3 coming from the symplectic Lie group Sp(6, ℂ) and the general linear group GL(4, ℂ) respectively. We give general formulas for their Hilbert series in terms of Lie theoretic data. We use them as key varieties (Format) to construct some families of polarized 3-folds in codimension 7 and 9. Finally, we list all the distinct weighted flag varieties in codimension (4 ⩽ c ⩽ 10.