In my project I am trying to locate a line in a list that is surrounded by other text.
So, I'm trying to make a command so that you can delete all the chats for the last hour.

Here's the script I've done:

when this sprite clicked
set (Clicked?) to [Y]
repeat until <not <[Chat] contains (Hour)?>
repeat until <<item (no.) of [Chat]> contains (Hour)?>
change (no.) by [1]
end
delete (no) of [Chat]
end

However, it only deletes lines that have only the “hour” variable in it, without any other text.How do I make it so that the script can locate a variable in a line with other text in a script?

You could just make it delete the whole history, which would be more practical and powerful.

If you still want to, you could try something like this. You will need a seperate list that holds the days since 2000 of each chat item.

set [i v] to [1]
repeat until <(item (i) of [timestamps v] :: list) < ((days since 2000) - ((1) / (24)))>
change [i v] by (1)
end
repeat (i) // i is the position of the first item further than a hour away.
delete (last v) of [chat v]
delete (last v) of [timestamps v]

Also, since you don't have any cloud variables in your project yet to make the chat work, you might want to put a note in the description stating that it isn't functional yet.