Based on the information you've provided, it sounds as if you want to create a CNAME Record, which should allow you to point to another domain, etc.
samba-tool dns add <Server_Name> <Zone_Name> <Alias_Name> CNAME <Target_Domain>
- samba-tool dns add: Initiates the command to add a new DNS record.
- Server_Name: The hostname of your Samba domain controller.
- Zone_Name: The DNS zone where you want to add the CNAME record
- Alias_Name: The name you want to use as the alias
- CNAME: Specifies that you are adding a CNAME (canonical name) record
- Target_Domain: The full domain name you want the alias to point to
Assuming "wsubu" Server is a Samba Domain Controller, you may want to try the following.
samba-tool dns wsubu.cn.lan cn.lan "wsubu" CNAME playground.cn.lan
If you run into Issues, you may want to read through the following Samba Article, which covers how to create AD ObjectGUID CNAME Records, etc.
https://wiki.samba.org/index.php/Verifying_and_Creating_a_DC_DNS_Record
In fact, the entire site is filled with useful Samba related information, along with the following Wiki Page.
https://wiki.indie-it.com/wiki/Samba