Creating a button in Inkscape

yes, there is possibility to create your own custom components, however it requires some knowledge of JavaScript.
Try to go through example "0301-10 Custom HMI Component" and modify it to act as a button with desired behaviour.

Core of the JavaScript will contain following code:

REX.UI.SVG.CustomButton = function(svgElem, args) {
    // Inherit from base component
    var that = new REX.UI.SVG.HTMLComponent(svgElem, args);
    var button = $(document.createElement('button'));            
    $(that.div).append(button);  
    return that;
};

Other functionality is up to you.

Hope it helps.

Regards, Tomas

Is there a possibility to create a custom button?
I would like to use my own svg graphics file as a button - when I click on it, it will temporary change a CNB element value.

Hubert