How can I ban Context Menu in Palette?Cannot add part Adornment (ContextMenu) Node#1836 (ContextMenu) Node#1836 (-6) to Diagram "u126" at the same time clicking on the left and right display context menus

Cannot add part Adornment (ContextMenu) Node#1836 (ContextMenu) Node#1836 (-6) to Diagram “u126” at the same time clicking on the left and right display context menus

That’s a bug that has been fixed in the most recent releases.

But the right thing to do is to make sure there’s no context menu shown in the Palette. The easiest way to do that when initializing the Palette is to disable the ContextMenuTool. Something like:

    $(go.Palette, . . .,
      { . . .,
        "contextMenuTool.isEnabled": false
      })

Add below code in showContextMenu() function

if (diagram instanceof go.Palette)
return;

Example:

function showContextMenu(obj, diagram, tool) {
// Show only the relevant buttons given the current state.
var cmd = diagram.commandHandler;
/*
document.getElementById(“cut”).style.display = cmd.canCutSelection() ? “block” : “none”;
document.getElementById(“copy”).style.display = cmd.canCopySelection() ? “block” : “none”;
document.getElementById(“paste”).style.display = cmd.canPasteSelection() ? “block” : “none”;
*/
document.getElementById(“delete”).style.display = (obj !== null && cmd.canDeleteSelection()) ? “block” : “none”;
document.getElementById(“componentConfig”).style.display = (obj !== null ? “block” : “none”);
//more such components

        if (obj instanceof go.Node) {
            //Setting selected component for further processing
            $scope.selectedComponent.category = obj.data.category;
            $scope.selectedComponent.key = obj.data.key;

        }
        if (diagram instanceof go.Palette)      //don't show context menu for palette elements
            return;
        // Now show the ,whole context menu element
        cxElement.style.display = "block";
        // we don't bother overriding positionContextMenu, we just do it here:
        var mousePt = diagram.lastInput.viewPoint;
        cxElement.style.left = mousePt.x + "px";
        cxElement.style.top = mousePt.y + "px";
    }

See Customizing context menu - #2 by walter