Hi Phuong Phan,
As for the SSH connection you are trying to establish, MySQL for Excel does not support opening a SSH tunnel on-the-fly as MySQL Workbench does, but you can trick this by creating the SSH tunnel yourself and create a connection to the tunnel.
Read this blog post about it:
https://blogs.oracle.com/mysql/guide-to-create-a-tunneled-ssh-connection-in-mysql-for-excel
Now about the Japanese characters, I performed a quick test and can create a table with Japanese characters using a charset of utf8_general_ci through an Export Data operation, and then I am able to do an Edit Data on that created table and add more rows with Japanese text and commit the changes. If I check the data in MySQL Workbench I see it correctly in Japanese. So I am not sure what is happening at your end.
Can you please check in MySQL Workbench the value of all the "character_set" variables (there are 8) and post them here? You can check them by going to "Status and System Variables" at the Management section in the left pane of a SQL Editor, and then go the "System Variables" tab within the Server Variables window, and filter by All.
Best regards.
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Javier Treviño
MySQL on Windows Team