style.css

/* Increase tab font size */
.tab {
    font-size:16px;
}


/* Main tabs container, copied from https://forum.vivaldi.net/topic/96664/merge-tabs-and-address-bar/42?lang=en-US&page=3 */
#tabs-tabbar-container {
    margin-left: calc(26vw + 100px);
    margin-right: 135px; /* Adjust to amount of extensions */
    transition: all .75s;
    padding-top: 0 !important;
}

#browser:has(.toolbar-mailbar:not(.toolbar-hidden)) #tabs-tabbar-container {
    margin-left: 47rem;
    margin-right: 0;
}

.win.normal .tab-group-indicator {
    top: -2px;
}

.win.normal #titlebar:not(.tabless) {
    top: -5px;
}

.UrlBar-AddressField {
    width: 26vw;
    transition: width .2s ease-in-out, height .2s ease-in-out, box-shadow 0.2s ease-in-out !important;
}

/* don't resize on focus
.UrlBar-AddressField:focus-within {
    width: 40vw !important;
    height: 30px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19), 0 6px 6px rgba(0, 0, 0, 0.23);
}
*/

.OmniDropdown {
    margin-top: -3px;
}

.mainbar .toolbar-mainbar:not(.toolbar-wrap .toolbar-droptarget) {
    position: absolute;
    top: 0;
    left: 34px !important;
    height: 30px;
    border-radius: 10px;
}

.mainbar .toolbar-mainbar {
    border-bottom: none !important;
}

.mainbar .toolbar-mainbar::before, .mainbar .toolbar-extensions::before {
    display: none;
}

.win.normal .mainbar .toolbar-mainbar {
    left: unset;
    right: unset;
}

.mainbar .toolbar-mailbar {
    width: 45rem;
}

.toolbar-mailbar .button-toolbar[title*="Seite"] {
    display: none;
}

/* Adjust extension position */
.toolbar-extensions {
    position: absolute !important;
    transform: translate(-100%);
    left: calc(100vw - 185px) !important;
    height: 30px !important;
    right: unset !important;
}

.window-buttongroup {
    height: 35px;
}

#browser:not(.is-settingspage) #main {
    position: unset;
}

#browser:not(.fullscreen) #header {
    height: 30px;
    min-height: unset !important;
}

.vivaldi {
    height: 34px;
    max-height: 34px;
    width: 34px;
    margin-top: 3px;
    border-radius: var(--radius) !important;
}

.vivaldi:hover{
    background-color: var(--colorAccentBgDark) !important;
}

.vivaldi .expand-arrow {
    display: none;
}

#browser.popup #header {
    height: 35px !important;
}

#browser.popup .UrlBar-AddressField {
    background-color: var(--colorBgLightIntense);
}

#browser.popup #pagetitle {
    margin-left: 45vw !important;
    padding: 10px 0 0 0 !important;
    max-width: calc(55vw - 220px) !important;
}

#browser.popup .toolbar-mainbar {
    left: 10px !important;
}

#browser.popup .UrlBar-AddressField, #browser.popu .UrlBar-AddressField:focus-within {
    width: 40vw !important;
}

#browser.popup .window-buttongroup button {
    height: 35px !important;
}

#browser.popup .toolbar-extensions {
    left: calc(100vw - 190px) !important;
}