Quick link to go to personal chat

How can I make a link to quickly go to a private chat with another user?
I tried to make a link to quickly go to a chat with a user, for example like this, https://mysite/chat/c/username/9 but it only works specifically in my case, and will not work for another user. Another user will not be able to follow the specified link. Since at the end of the link you need to change the value “9” - it is individual for everyone.

I also wanted to make a quick link to the chat with a ready-made message template similar to personal messages

I don’t believe this is the case.

If Alice and Bob have a direct message with each other, Alice will see /chat/c/bob/9 and Bob will see /chat/c/alice/9. The slug is ignored, so Alice will arrive in the same place even if she clicks a link like /chat/c/alice/9. You could use a link like /chat/c/-/9 if sharing among the group to make that more clear.