After upgraded to macOS Big Sur(11.0.2),  i found out that newly created file by Qt Creator(4.13.1) in a QT project will not show in "Unstaged files" Window, but it will work normally if the new file are been created with other editor like "Sublime Text", or move it to the folder manually.

And in the mean time, it will always show in the terminal by "git status":

I don't know if it's related to the macOS upgrade, since i just discover it recently.