How to always show sort arrrows?

By default free jqGrid shows arrows only on a sorted column. I need to show arrows always. I can alter CSS like

  .ui-jqgrid .ui-jqgrid-sortable .s-ico {
    display: inline-block !important;
  }

, but I suspect there is an option for this.

jqGrid has viewsortcols option (see old documentation), which is supported by free jqGrid too. The default value of the option is viewsortcols: [false, "vertical", true]. The first value of viewsortcols array specifies whether the sort icons should be shown always or not. Thus to implement your requirements you need just add the option

viewsortcols: [true, "vertical", true]

See https://jsfiddle.net/OlegKi/L417gcwf/72/ for example.

If you have an interest for more advanced customizing features of free jqGrid you can find in "UPDATED" part of the answer for example.