Map width is controlled in your Shopify theme editor.
Which place you edit depends on how your map was installed:
Express setup: edit stockists map embedCustom setup: edit stockists map sectionIf you are not sure which setup you used:
Express mode or Custom mode.Express setup uses Shopify embed.
Steps:
Online Store -> Themes.Customize.App embeds or the embed area for your theme.Stockists map embed.