Design option is not there, only live.

If you must use the Legacy FGLayouts, you could drop back to an older version of DW before design view was disabled in 2014.

As a workaround, you could open your CSS code in Code View and add an X as shown below.  DO NOT USE CSS DESIGNER PANELS for this.  It won't work.

/*

    Dreamweaver Fluid Grid Properties

    ----------------------------------

    dw-num-cols-mobile:     X 4;

    dw-num-cols-tablet:        8;

    dw-num-cols-desktop:    12;

    dw-gutter-percentage:    25;

=====================================

Save. Close DW, re-open DW.  This will trick DW into thinking it's a normal layout so you can use Design View.

#1 You must be using the legacy Fluid Grid Layout feature that was subsequently removed from DW CC.

Design view is disabled in Fluid Grid Layouts.   Use Bootstrap. It's better for a lot of reasons.  

#2 Image Maps are not responsive.  The hotspot coordinates don't resize to fit responsive images and will drift out of place in smaller devices.   Best advice is to avoid using image maps if you can.

when you click on design or live, don't you have a pop up , as in this video ... 10.15.2017-08.39.14