I have tried to rename the upper left button's text from My_first_blog while resulted in vain.
The attribute of website: title in _quarto.yml seems has nothing to do with the text in that button.
Well, the actual issue is that no change has been made, no matter how many times I edit the .qmd file and hit the render button. I fixed this issue by manually closing all the file tabs in my Rstudio and then rendering the index.qmd for one more time.
I believe there are some background sessions hidden behind the Rstudio ui. I think that's why Rstudio and R language are not my favorite coding options.
Now you can tell the difference I was talking about. The rendered website based on the docs directory remaining at the old version.
And if you clone the whole repository and render the index.qmd from the root directory, you can see the text in the upper left button has been changed from My_first_blog to My first blog.
The reason to this difference is still mystic to me.
Now the website seems rendered functionally after several minutes. The reason may be because of the cache updating frequency of the github server. Interesting.