selecting multiple blocks in an editor

When selecting multiple blocks in an editor, it doesn't allow for selecting part of the text within a specific block; instead, it selects the entire block. I tested a similar feature in Notion, as shown in the figure below. How can I achieve this functionality? I also noticed that there is a "New cross-block selection" feature mentioned in the roadmap, and I am not sure if this refers to the functionality I need. I am really looking forward to updates regarding this feature in the roadmap.