Техподдержка ответила:
	
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			 Цитата: 
		
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		You should be able to define in your app.json:
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"builds": {    "classic": {
        "toolkit": "classic",
        "theme": "theme-triton",
        "sass": {
            // "save": "classic/sass/save.json"
        }
    },
    "modern": {
        "toolkit": "modern",
        "theme": "theme-neptune",
        "sass": {
            // "save": "modern/sass/save.json"
        }
    }
},
Источник: https://www.sencha.com/forum/showthr...=1#post1121208