Changing directories names

Hello,

Is it safe to change app/plugins and app/themes directories to something like app/modules and app/templates ?

I believe that changes should be done in composer.json ?

You can only rename them if WordPress supports it. You can look into constants like WP_PLUGIN_DIR and WP_PLUGIN_URL.You could use this for themes:

register_theme_directory( '/path/to/templates' );

composer.json will need to be updated and maybe in other places as well.

My suggestion: stick to the default names.