CAUTION!!
You are discussing Master-Master replication but calling it Master-Slave replication.
In the latter, Slaves pull changes from the Master. The Master never pulls changes from Slaves.
The setup @avc references is Master-Slaves. It’s purpose is to have continuous replication across the Internet to 100% distinct Slave environments (different hosting service, different backbone, different electricity, different political jurisdiction, etc). In the event of failure of the Master any one of the Slaves can be used immediately as the new main server.
In that setup, data availability on the Slaves may end up delayed a few seconds. That is totally unacceptable for the Master-Master replication you are looking for.
To achieve what you want, you need to discover, What is MariaDB Galera Cluster?
I have no need of such a thing, so I have not tried it.
You might want to look at ERPNext High Availability using Galera cluster
Despite the above, it seems as though you are using ERPNext as though it is a desktop app like Microsoft Word where you need a copy in every machine. It is not like that. You can have hundreds of users connected to one copy of ERPNext using any browser.
You can rent a Virtual Private Server (VPS) anywhere on the Internet, such as Digital Ocean, Go Daddy, whatever, install ERPNext on it and connect to it from your laptop, with no need for an ERPNext installation on your laptop.