Expand macro does not nest more than one level

Expand macro does not accept more than one nesting level in markup inserting dialog (check attached).

The next markup assumed to be 4 levels, while it is rendered in preview and a mix of level not further than second level. Meanwhile after adding such macro, it is possible to drag & drop Expand sections in page content editor to achieve required result.

\{expand:Level1\}
    \{expand:Level2\}
        \{expand:Level3\}
            Level4 reached!
        \{expand\}
    \{expand\}
\{expand\}