What is the role of scene item.selected set to true

[hamburger-l]

When I read the streamlabs-obs project, I found that setting the selected of the scene item to true will add the corresponding select box, but I cannot reproduce it after the same operation

https://github.com/stream-labs/streamlabs-obs/blob/master/app/services/selection/index.ts#:~:text=sceneItems%20are%20selected-,scene,%7D)%3B,-%7D

[n3g2]

OBS_content_setShouldDrawUI(displayId, true);

Solved the problem of marking display, but can't drag...

@bbc-594