I do not believe that something that is supposed to be so simple is not possible.
I want to build a chat with a sprite background, if i use textbox i can work with the scrollbar but I have to use plain text because it has a transparent background and i have the option to format the text. But I found no way to do it.
There are a lot of questions on the forum about the scrolling but they are very old and all the examples and links are not working and neither they are not for Text object.
I would love to get any idea that will help me.
Hmm.. When i do for example a list for my highscores, i create a text object at each rank, and i add an instance variable called ID.
Then i just do on arrow down click "add +1 to id", when arrow up i "substract -1 from id", this way the ids on the text object will change and so does the text(if you set text to spawn on certain id). - Same could be done for a scrollbar, if you somehow check the scrollbars movement and add it to the ID of the textobject.
When textbox, you can use CSS to change for example background image, text style, image, all that.
But i never used scrolling with textbox, not sure if this helps you at all, just giving a tip.