actually you can make it dynamic length by override esri-popup style, you can try adding this style to your custom CSS file : .esriPopup .sizer { width: 104% !important; }
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The easy way to fix this problem by change attribute name display size to fit popup default width (ex:change attribute "Public_Holiday_Status_AR" to "Open in Holiday"). Also you can override .esri-popup style in (esri main.css)
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