Embed SMS body in rcmobile href

I'm looking to embed text in the rcmobile href such that it prepopulates directly in the Ring Central Softphone.

Basically, I have a button on my application with the following code:

<a href="rcmobile://sms?number=xxx&body=test"

I would like pressing that button to

1. open up the Softphone,
2. populate xxx as the number,
3. and populate 'test' as the text.

Then the user can just press send to send off the SMS message. It does steps 1 and 2, however, it does not do step 3.

Is there a way to also do step 3?

I am aware of https://forums.developers.ringcentral.com/questions/1380/ringcentral-embeddable-sms-pass-the-message-after.html, however, on macOS the sms:// is not available as it just opens the iMessage app.

Thanks!