You change it through the very same interface you provided the screenshot of - but you have to do this as a member of the local Administrators group and run the process in the elevated mode (i.e. bypass the User Account Control restrictions). You can also do this via PowerShell.
More at https://learn.microsoft.com/en-us/answers/questions/1179601/change-computer-name-and-netbios-internet-protocol and https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.management/rename-computer?view=powershell-7.4
The NetBIOS name is limited to 15 characters - that's imposed by the operating system and cannot be increased
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hth
Marcin