App Store Connect / iTunes Connect wider App Screen by hiding navigation. Suggested use with JavaScript injection extension for your browser.

appstoreconnect_navigation_toggle.js

function toggleNavigation() {
    var topPane = document.getElementById("appPageHeader");
    var leftPane = document.getElementsByClassName("pane-layout-sidebar")[0];
    var bottomPane = document.getElementsByClassName("pane-layout-content-header")[0];
    var bottomPaneHeader = bottomPane.getElementsByClassName("pane-layout-content-header-text")[0];
	
    var displayType = (topPane.style.display === "none") ? "block" : "none";
    topPane.style.display = displayType;
    leftPane.style.display = displayType;
    //NOTE: Uncomment this line if you want to hide `Save` and `Submit` buttons, and remove the next two lines
    // bottomPane.style.display = displayType == "block" ? "flex" : "none";  
    bottomPane.style.padding = "3px";
    bottomPaneHeader.style.display = displayType;
}

function addToggleButton() {
    var button = document.createElement("Button");
    button.onclick = toggleNavigation;
    button.innerHTML = "Toggle";
    button.style = "top:8px;right:255px;position:fixed;z-index:99999;";
    document.body.appendChild(button);
}

addToggleButton();