trilium/src/public/app/widgets/spacer.js

import BasicWidget from "./basic_widget.js";
import contextMenu from "../menus/context_menu.js";
import appContext from "../components/app_context.js";

const TPL = `<div class="spacer"></div>`;

export default class SpacerWidget extends BasicWidget {
    constructor(baseSize = 0, growthFactor = 1000) {
        super();

        this.baseSize = baseSize;
        this.growthFactor = growthFactor;
    }

    doRender() {
        this.$widget = $(TPL);
        this.$widget.css("flex-basis", this.baseSize);
        this.$widget.css("flex-grow", this.growthFactor);
        this.$widget.css("flex-shrink", 1000);

        this.$widget.on("contextmenu", e => {
            this.$widget.tooltip("hide");

            contextMenu.show({
                x: e.pageX,
                y: e.pageY,
                items: [
                    {title: "Configure Launchbar", command: "showLaunchBarSubtree", uiIcon: "bx bx-sidebar"}
                ],
                selectMenuItemHandler: ({command}) => {
                    appContext.triggerCommand(command);
                }
            });

            return false; // blocks default browser right click menu
        });
    }
}