trilium/apps/client/src/widgets/Breadcrumb.css

.breadcrumb-row {
    position: relative;
    height: 30px;
    min-height: 30px;
    align-items: center;
    padding: 10px;
    container-type: inline-size;

    @container (max-width: 500px) {
        .breadcrumb-badges {
            flex-shrink: 0;

            >* {
                flex-shrink: 0;
                width: 18px;
            }

            .dropdown {
                button {
                    flex-shrink: 0;
                }
            }

            .breadcrumb-badge {
                flex-shrink: 0;
                padding: 0 2px;

                >* {
                    text-overflow: clip;
                }

                .text {
                    display: none;
                }
            }
        }
    }
}

body.experimental-feature-new-layout .breadcrumb-row {
    padding-inline-end: 0;
}

.component.breadcrumb {
    contain: none;
    display: flex;
    margin: 0;
    align-items: center;
    font-size: 0.9em;
    gap: 0.25em;
    flex-wrap: nowrap;
    overflow: hidden;
    max-width: 85%;

    > span,
    > span > span {
        display: flex;
        align-items: center;
        min-width: 0;

        a {
            color: inherit;
            text-decoration: none;
            min-width: 0;
            max-width: 150px;
            text-overflow: ellipsis;
            white-space: nowrap;
            overflow: hidden;
            display: block;
            flex-shrink: 2;
        }
    }

    > span:last-of-type a {
        max-width: 300px;
        flex-shrink: 1;
    }

    ul {
        flex-direction: column;
        list-style-type: none;
        margin: 0;
        padding: 0;
    }

    .dropdown-item span,
    .dropdown-item strong {
        text-overflow: ellipsis;
        white-space: nowrap;
        overflow: hidden;
        display: block;
        max-width: 300px;
    }
}