Is it possible to expand and collapse by clicking on Title?

Yes, that would be a great improvement. Ideally, it should be possible to make for example an image field (thumbnail) and title field be the clickable element, replacing the icon.

Thinking more about this, it could just be the Title field which is always used, since you could add an image field before the title field, hide the image field, and then insert the image via its token, in the rewrite part of the Title field.

Adding my vote, please

I came here to ask for the same thing. I assumed I might be able to accomplish something like this by theming the views-view-collapsible-list.html.twig file, but all of the Views-supplied fields are grouped together there.

Adding my vote! Would really add to the functionality.