Http request node after update ignores line break character "\n"

Hello! I have been actively using Node RED for a very long time. My device is Raspberry 3 not updated for over three years. There Node RED v1.3.7. I am using Http request node to send webhook messages to messenger. Specifically Synology Chat. And it works fine now, but on the old version. I installed Node RED v3 to a new device and the code doesn't work anymore.
This is what the query string looks like:

http://192.168.1.5:5000/webapi/entry.cgi?api=SYNO.Chat.External&method=incoming&version=2&token=%Ao0td3NxTaqh4o3FrOR6kXl%&payload={"text": "Hello+world"}

Thus, I send the message "Hello world" to the channel corresponding to the token in url.

I have large messages, some of them look like tables, and for this it is necessary to use line breaks.
And in the new version when I send "mymessage" texts come without formatting

payload={"text": "{{{mymessage}}}"}

****
msg.mymessage = msg.1 + '\n' + 'my text \n' + msg.2

And this is observed only on the updated version. The old version works, and skips the line break character.
But if I do this:

payload={"text": "Text1\nText2\nText3"}

then the line break is transmitted normally both in the old and in the new version of Node RED. But in this case, I can't use variables.
It turns out that brackets {{{...}}} eat the line break character in the new version of Node RED.
Any ideas how to solve the problem?