I have a toml file:

["\"foo\""]
"\"bar\"" = "\"baz\""

yj -tj <a.toml failed with:

Error parsing TOML: (1, 2): invalid table array key: invalid bare key character: \

According to the TOML specification:

• The escape \" is valid in basic strings. (https://toml.io/en/v0.5.0#string)
• Quoted keys follow the exact same rules as either basic strings or literal strings. (https://toml.io/en/v0.5.0#keys)
• Naming rules for tables are the same as for keys. (https://toml.io/en/v0.5.0#table)