obsidian.css.masonry.tabs.css

body {
    /* Fit 2 per screen = 930px ... 3 = 620px */
    --masonry-split-widths: 930px;
    --tab-stacked-pane-width: var(--masonry-split-widths);
}

div.workspace-split.mod-root {
    overflow: auto;
}

/* Need this for any panes scrolled off screen to be able to drag tabs properly */
div.workspace-split.mod-root>div.workspace-split.mod-vertical {
    width: unset;
}

div.workspace-split.mod-root>div.workspace-tabs,
div.workspace-split.mod-root>div.workspace-split.mod-vertical>div.workspace-tabs,
div.workspace-split.mod-root>div.workspace-split.mod-vertical>div.workspace-split.mod-vertical,
div.workspace-split.mod-root>div.workspace-split.mod-vertical>div.workspace-split.mod-horizontal,
div.workspace-split.mod-root>div.workspace-split.mod-horizontal,
div.workspace-split.mod-root>div.workspace-split.mod-horizontal>div.workspace-split.mod-vertical,
div.workspace-split.mod-root>div:only-of-type.workspace-split.mod-horizontal>div.workspace-split.mod-vertical>div.workspace-tabs,
div.workspace-split.mod-root>div.workspace-split.mod-horizontal>div.workspace-split.mod-vertical>div.workspace-split.mod-horizontal {
    min-width: var(--masonry-split-widths);
}

div.workspace.is-right-sidedock-open div.sidebar-toggle-button.mod-right,
div.workspace:not(.is-right-sidedock-open) div.sidebar-toggle-button.mod-right {
    position: fixed;
    right: var(--frame-right-space);
    background-color: var(--background-secondary-alt);
    border-bottom: var(--divider-width) solid var(--divider-color);
    z-index: 1;
    padding: 0px;
    height: 40px;
}

div.workspace.is-right-sidedock-open div.sidebar-toggle-button.mod-right>div.clickable-icon,
div.workspace:not(.is-right-sidedock-open) div.sidebar-toggle-button.mod-right>div.clickable-icon {
    padding: 0px 12px 0px 12px;
    border-radius: 0px;
}

body>div.titlebar>div.titlebar-inner>div.titlebar-button-container.mod-right {
    background-color: var(--background-secondary-alt);
    border-bottom: var(--divider-width) solid var(--divider-color);
    height: 40px;
}

body:not(.is-focused)>div.titlebar>div.titlebar-inner>div.titlebar-button-container.mod-right,
body:not(.is-focused) div.workspace.is-right-sidedock-open div.sidebar-toggle-button.mod-right,
body:not(.is-focused) div.workspace:not(.is-right-sidedock-open) div.sidebar-toggle-button.mod-right {
    background-color: var(--tab-container-background);
}

.is-hidden-frameless:not(.is-fullscreen) .workspace-tabs.mod-top-right-space .workspace-tab-header-container:after {
    position: fixed;
    width: calc(var(--frame-right-space) + 42px);
}

.is-hidden-frameless:not(.is-fullscreen) .workspace-tabs.mod-top-right-space .workspace-tab-header-container {
    padding-right: calc(var(--frame-right-space) + 42px);
}

body:not(.is-popout-window):not(.is-grabbing):not(.is-fullscreen) .workspace-tabs.mod-top .workspace-tab-header-spacer {
    -webkit-app-region: no-drag;
}

body:not(.is-popout-window) div.side-dock-actions:before {
    content: "\2723";
    font-size: 30px;
    -webkit-app-region: drag;
    text-align: center;
    margin-left: 1px;
}

/* COMMENT OUT BELOW IF YOU DO NOT WANT THE BACK/FORWARD BUTTONS ADDED TO THE LEFT RIBBON */
body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-forward,
body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-back {
    display: inline;
    position: fixed;
    left: 0;
    width: 43px;
    padding: 0;
    margin: 0;
    text-align: center;
    height: 26px;
}

body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-forward {
    bottom: 105px;
}

body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-back {
    bottom: 140px;
}

body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-forward>span.history-counter,
body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-back>span.history-counter {
    display: none;
}

body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-forward>svg,
body.is-hidden-frameless:not(.is-popout-window) .titlebar .titlebar-button.mod-back>svg {
    vertical-align: middle;
    width: 20px;
}

I played around for a while but couldn't figure it out. If I hear anything, I'll let you know. Not your fault, of course, but the first obsidian snippet I've come across that behaves differently on Windows and macOS. lol

For the time being on the mac, I used Commander to add forward/back buttons to the ribbon. I'd rather them down above the vault picker (like your snippet) but that's for another day. Anyway, thanks again.