If element is present in list!

hello everyone.
I have a simple list like the blocks that I attach where I add elements.
can someone help me to perform the check when I add to see if the same element is already present in the list?
if it is already present I would not like to add a new element while if it is not present I would like to add it.
thanks to anyone who helps me.
image

Is in list block. Use this with the not block.

I don't know how to use it, can you help me please?

this doesn't work

Try this:

image

this doesn't help me.
I'm adding names to a list and if I try to insert a name that already exists it should warn me that the name already exists and it shouldn't add it.

image

it doesn't work for me

Why not tell us "what doesn't work" ...



Sample run

closing, also asked in Kodular, just wastes everyone's time.