Hi Huang,
It is name property instead of label property, thus the change won't be applied to timeline section.
To the best of my knowledge, the text/title of timeline couldn't be modified, it is front-side behavior and by design in UCI.
Due to the Timeline element has a recognizable id value,

thus we could change the text with unsupported javascript code,
it will execute at form OnLoad event and wait 2 seconds for form being completely loaded,
then get the timeline element by document.getElementById function to change its text.
function onFormLoad() {
setTimeout(function() {
if (parent.document.getElementById('action_bar_header_title')) {
parent.document.getElementById('action_bar_header_title').innerText = 'Timeline_123';
}
}, 2000);
}
Modification:

Regards,
Clofly