New line in basic card in google actions

Markdown requires that to force a line break, you need two spaces followed by a newline. So something like this in your code should work:

app.ask(app.buildRichResponse()
        .addSimpleResponse("Simple response")
        .addBasicCard(app.buildBasicCard("L1  \nL2  \nL3")
)

To be clear, that is <space><space><backslash><n>

For me works a double space enclosed by a \n

\n  \n

A limited subset of markdown is supported in google actions:

A new line with a double space like you content \n(content with the newline)

for bold **bold**

and for italic *italics*

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