what is the line with the numbers above staff called?

hi, what is the line with the numbers above staff called? is there a way to disable it? sometimes I can accidentally remove a bar pressing it
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The line is called system track. Alt + T is the default shortcut for showing/hiding it.
see

And you can do cool things with it - for example you can shorten a bar without affecting what comes next.

after selecting some beats try clicking the bin icon.

thank you very much!