My view on this is that if they worked, they'd be prescribed (on the basis of being almost risk-free.)
No, they don't work and many specialist consultants will tell you that you are wasting your money. The vitamin industry is a huge 'scam' as most people don't need any extra if they eat a healthy diet.
Heavy periods won't be helped by vitamins. (You might want to think about a Mirena coil if they are really bad and increase your iron intake.)
Unless someone has a limited diet, then food provides all the vitamins needed (Vit D being an exception.)
If you read the ingredients in many of these meno supplements, you are most likely getting all the vitamins anyway through your food without needing to take a tablet. There's also the view that there may be other things in the 'whole food' that can't be replicated by a tablet - fibre, for example.
Excess vitamins are excreted (like Vit B & C) and excess of Vit A and D are stored in the liver (so too much is actually toxic.)
Some of these meno supplements have herbs added - like sage and maybe plants like soya - but if you want to deal with hot flushes, it's better to buy those separately - for example sage tincture, eat soya as yoghurt or tofu. etc.