Although Plantuml supports "compact nested mapping" for simple maps:
e.g.
@startyaml
A:
-
B:C
D:E
@endyaml
can be compacted as:
@startyaml
A:
- B:C
D:E
@endyaml
... this doesn't extend to block mapping:
e.g.
@startyaml
A:
-
B:
C:D
E:F
@endyaml
doesn't compact to:
@startyaml
A:
- B:
C:D
E:F
@endyaml
But I believe that is valid YAML syntax, as found in the wild in question https://forum.plantuml.net/12946/bug-in-new-yaml-parser