I can't, there's a *** rule from the initial component scss  https://github.com/PrestaShop/PrestaShop/blob/46510cc8cfaa1f995dff6bc92e485914f8e57d40/admin-dev/themes/new-theme/scss/components/_toggable_field.scss#L48    It overrides all the width value, including some in-style value that seems to be computed by JS. This is a pain...