@jsulm, I apologize, I should've mentioned it in the original post: one of the requirements of the project is that we can not use any 3rd party library for the text editor, except for Qt.
From what I see in the QScintilla github, it is ported to Qt on top of the TextEdit widget, so I will look further into their implementation to figure out how they've done it.

@Yash001 said in which container (Qvector or QList) is good to use for insert, delete, and access the last element.:

I am adding data point at last position of container, and only accessing the last element of container. So which is better container?

It's what we call Last In First Out ( LIFO) queue.
So QStack seems an obvious candidate.

QStack inherits from QVector.

@SGaist Thanx mate