YouTube.com "big theater mode" injection. Gives the video full height when in theater mode.

youtube_big_theater_mode_injection.js

(function() {
    var coverNavBar = true;
    
    var css = `
        ytd-watch:not([fullscreen])[theater] #player.ytd-watch {
            height: ` + (coverNavBar?'':'calc(') + '100vh' + (coverNavBar?'':' - 56px)') + ` !important;
            max-height: none !important;` + (coverNavBar?`
            position: relative;
            margin-top: -56px;
            z-index: 9999;
            `:'') + `
        }`;
    
    if (coverNavBar) {
        css += `
            ytd-page-manager, ytd-watch {
                overflow: visible !important;
            }
        `;
    }
    
    var cssDiv = document.createElement('div');
    cssDiv.innerHTML = '&shy;<style>' + css  + '</style>';
    document.body.appendChild(cssDiv.childNodes[1]);
})();

youtube_big_theater_mode_injection_instructions.md

• How to show navigation bar: set var coverNavBar = true; to var coverNavBar = false;.
• How to create bookmarklet: Visit https://mrcoles.com/bookmarklet/ and paste the below youtube_big_theater_mode_injection.js code into the javascript input box.
• How to directly inject into website: Type javascript: into the url field, followed by the below youtube_big_theater_mode_injection.js code.

Known Bugs:

• If already in "Theater Mode", the video wont properly scale, you need to exit and re-enter "Theater Mode" or enter and exit "Fullscreen" mode to fix the scaling issue.