Best toys for a 21 month old

[AiredaleFan]

My lttle girl (21 months) seems to have become bored with the toys she has to play with - she has had them for some time and I'm thinking she needs ones that are more mentally stimulating for her age. She has a little kitchen that she plays with a fair amount, she likes to wheel a little buggy around and menace the dog with it, and she likes duplo but only if there is someone building it with her, also jigsaws. The difficulty is finding something that she will play with alone for a short time while I am trying to have a shit cook. Everything else that she used to enjoy is now being ignored, and I'm having to resort to sticking her in front of the TV which I don't want to do.

Any suggestions? Ideally she needs things she will play with alone for short periods of time.

Chalkboard, chalk and a little cloth.
Stringing macaroni onto a string ‘necklace’ was a recent favourite
Playdough-with roller and cutters (can be done on a big chopping board on kitchen floor)
Stacking cups still a favourite
We have a load of wooden fruit that velcros together-chopping that with a toddler knife to make ‘soup’ is popular. Fruit was from aldi but seen it other places.

Also a little toolset-there’s a nice one by Melissa and Doug and it’s very portable which is always handy

Sticking stickers on a piece of paper!!

Thanks all for your suggestions. I especially like the chalkboard idea as she loves drawing. Haven't gone down the stickers or play doh route, but maybe it's time... Many thanks.