zotero/scss/components/_selectItemsDialog.scss

#zotero-select-items-dialog {
    display: flex;
    min-width: 800px;
    min-height: 450px;
}

#select-items-dialog {
    padding: 0;
    appearance: none;
    background: var(--material-background);

    #collections-items-container {
        flex: 1 1 auto;
    }

    #zotero-select-items-container {
        display: flex;
        flex-direction: column;
    }

    #zotero-collections-tree-container {
        min-width: 200px;
		min-height: 100%;
        padding: 16px 0;
        background: var(--material-sidepane);
        border-inline-end: var(--material-panedivider);
    }

    #zotero-collections-tree {
        background: var(--material-sidepane);
    }

	#zotero-items-pane-content {
        // Please do not become infinitely tall
		min-height: 0;
        flex: 1;
        flex-basis: 0;
	}

    #search-toolbar, .dialog-button-box {
        padding: 16px;
    }

    #search-toolbar {
        display: flex;
        flex-direction: row;
        justify-content: flex-end;
        flex: 0 0 auto;
    }
    
    .dialog-button-box {
        gap: 8px;
        
        button {
            margin: 0;
        }
    }

    #zotero-items-pane-content, .dialog-button-box {
        border-top: var(--material-border-quarternary);
    }
    
    // Draggable areas:
    #zotero-collections-tree-container,
    #search-toolbar,
    .dialog-button-box {
        -moz-window-dragging: drag;
    }

    // Non-draggable sub-areas:
    #zotero-collections-tree-container .windowed-list,
    #search-toolbar quick-search-textbox,
    .dialog-button-box button {
        -moz-window-dragging: no-drag;
    }
}

// richlistbox elements are crazy and will expand beyond the window size
// unless all/most elements in the hierarchy that contain that
// richlistbox have a min-height: 0 set
.contain-richlistbox {
    @include contain-richlistbox;
}