Question: Use arrow keys to move blocks in canvas configured in absolute positioning mode

No, unfortunately, for such a case, the custom keymap would be the only solution. You should just get the selected component and update its style.

I have found a working solution for this as follows:

grapesjs.init({
    keymaps:  {
       defaults: {
         "ns:up" : { keys: 'up, shift+up', handler: 'moveUp' },
         "ns:down" : { keys: 'down, shift+down', handler: 'moveDown' },
         "ns:left" : { keys: 'left, shift+left', handler: 'moveLeft' },
         "ns:right" : { keys: 'right, shift+right', handler: 'moveRight' }
        }
     },
...

The commands are being added as follows:

editor.Commands.add("moveUp", { run: function(editor) { moveSelectedElement(editor, -5, "top"); }});
editor.Commands.add("moveDown", { run: function(editor) { moveSelectedElement(editor, 5, "top")}});
editor.Commands.add("moveLeft", { run: function(editor) { moveSelectedElement(editor, -5, "left")}});
editor.Commands.add("moveRight", { run: function(editor) { moveSelectedElement(editor, 5, "left")}});

The moveSelectedElements method just does the following:

function moveSelectedElement(editor, pixel, property) {
        var model    = editor.getSelected();
        var style    = model.getStyle();
        var position = style[property].replace('px','').replace(' ', ''); 
        
        // Round to nearest multiple of 5 to align to grid
        var newPosition = Math.ceil((Number(position)+Number(pixel))/5)*5
        style[property] =  newPosition + "px";
        
        model.setStyle(style);
        editor.trigger('component:toggled');
    }

However, when moving the elements with arrow keys, the canvas scrolls as well, which is the default bowser behaviour.

How can we prevent the default propagation with the keymaps (e.preventDefault())? Should this be happening automatically, or is there a way to configure that?

keymaps.add('ns:my-keymap', '⌘+s, ctrl+s', 'some-gjs-command', { // Prevent the default browser action prevent: true, });