Thanks, that icon is missing for me. I have to check out if this is a theme or snippet related issue with my setup.
Collapsed by default would be a plus but I think that will be doable with a snippet.
EDIT: Found it. When using the Minimal theme there is a new option under Style Settings > Minimal > Properties > Hide properties heading which is enabled by default. It hides the heading together with the collapse arrow >.
Got it. We can change the post title later if need be.
Minimal had the Properties label and collapse icon hidden for a few versions but reverted to it being shown. If you are using Minimal, update it, and have a look in the Minimal Style Settings options; there are a few toggles for Properties.