Question

I found library: geometrycontrols that is written to api v2 and allows adding buttons. How to make a toggle button to add a marker in the api v3? I have initiated map etc.

Answer 1

You can add an arbitrary structured <div> to the map:

var control = document.createElement('div'); 

You add a listener to this control or to its children, e.g.:

google.maps.event.addDomListener(control, 'click', function() {...}); 

You position the control on the map:

control.index = 1;   
map.controls[google.maps.ControlPosition.TOP_RIGHT].push(control);  

For details, see:

Custom Controls

Example