At that age my DD liked:
— fruit bubble tea kit
— marble run
— board games, eg. Dobble, Monopoly, Cluedo, Uno, Taco Cat Goat Cheese Pizza (or whatever it’s called), Throw Throw Burrito, Sussed etc.
— stationery: notelets, stickers, pens, glow in the dark and glitter gel pens, nice pencil sets eg. from Faber Castell, paper and notebooks. Djeco do some great writing sets and Smiggle stationery was big for that age group. If you DD likes cats, Tesco bought out Paperchase and they have some very cute ranges with animals in bigger Tesco stores.
— a big hit with DD at that age was a lovely musical jewellery box - Djeco have some really gorgeous ones!
— a make your own bath bomb kit
— crystal growing kit
— gemstones set
— all kids that age love Jellycats (but Squishmallows are cheaper!)
— crafts like a French knitting dolly, a weaving loom and first sewing kits
— flower press
— lots of jewellery making kits. A cheapo box kit of beads and elastic string went down very well (you can find these on Amazon, eBay etc.)
— DD was into loom bands at 6 but that fad may have just passed!
— at 6 DD still liked dressing up clothes, especially some of the posher Disney Princess costumes like Belle; and butterfly wings
— Lego, Lego and more Lego
— DD also liked Little Live pets, at 6 the bird in particular; and also the clockwork hamsters in plastic balls which are from a different brand, I forget the name but you can get them in The Entertainer
— for inspiration, look at Rex London which has loads of stuff perfect for this age