When using the [details] tag to hide content (on the little gear, which brings up the Options tab), be sure there is a blank line before the section (when viewed in your editor).
For example, a details link on the same line:[details=Summary]This text will NOT be hidden[/details]
A details link on the next line:
Summary
This text will be NOT be hidden
A details link, with a blank line above it:
Summary
This text WILL be hidden
It also works to chain these together without a space in between
This text will be hidden
Note that all of these examples show up as hidden in the “preview” pane.