Make a default tamplet

After I make customizing change to my layout, I want to use it for any xml file that i import

Sure, just save it as a different file name, Select All and delete, and you should be good to go.

I set the blank file to “read-only” so I don’t accidentally overwrite it.

I did what you say select all and delete it, Then I save the file with a new name. I reopen the file and Import the musicxml then a new window pup “Flow Import option” I try all but there no music note was import to my custom layout

Just hit OK, what happens? That’s the normal XML import window.

Once you’ve imported your MusicXML file as a new flow, make sure that flow is assigned to your custom layout in Setup mode. That procedure is described in the operation manual here.