Restore cell insertion indicator color token

src/vs/workbench/contrib/notebook/browser/media/notebook.css

@@ -443,7 +443,6 @@
 	left: 0px;
 	right: 0px;
 	opacity: 0;
-	/* transition: opacity 0.2s ease-in-out; */
 	z-index: 10;
 }
 

src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts

@@ -1332,6 +1332,13 @@ export const cellStatusBarItemHover = registerColor('notebook.cellStatusBarItemH
 	hc: new Color(new RGBA(255, 255, 255, 0.15)),
 }, nls.localize('notebook.cellStatusBarItemHoverBackground', "The background color of notebook cell status bar items."));
 
+export const cellInsertionIndicator = registerColor('notebook.cellInsertionIndicator', {
+	light: focusBorder,
+	dark: focusBorder,
+	hc: focusBorder
+}, nls.localize('notebook.cellInsertionIndicator', "The color of the notebook cell insertion indicator."));
+
+
 registerThemingParticipant((theme, collector) => {
 	collector.addRule(`.notebookOverlay > .cell-list-container > .monaco-list > .monaco-scrollable-element {
 		padding-top: ${SCROLLABLE_ELEMENT_PADDING_TOP}px;
@@ -1448,6 +1455,11 @@ registerThemingParticipant((theme, collector) => {
 		.monaco-workbench .notebookOverlay .monaco-list .markdown-cell-row.focused { box-shadow: 0px 2px 8px 2px ${cellShadowColor} }`);
 	}
 
+	const cellInsertionIndicatorColor = theme.getColor(cellInsertionIndicator);
+	if (cellInsertionIndicatorColor) {
+		collector.addRule(`.notebookOverlay > .cell-list-container > .cell-list-insertion-indicator { background-color: ${cellInsertionIndicatorColor}; }`);
+	}
+
 	// Cell Margin
 	collector.addRule(`.notebookOverlay .cell-list-container > .monaco-list > .monaco-scrollable-element > .monaco-list-rows > .monaco-list-row  > div.cell { margin: 0px ${CELL_MARGIN}px 0px ${CELL_MARGIN}px; }`);
 	collector.addRule(`.notebookOverlay .cell-list-container > .monaco-list > .monaco-scrollable-element > .monaco-list-rows > .monaco-list-row { padding-top: ${EDITOR_TOP_MARGIN}px; }`);
@@ -1459,7 +1471,6 @@ registerThemingParticipant((theme, collector) => {
 	collector.addRule(`.notebookOverlay .markdown-cell-row .cell .cell-editor-part { margin-left: ${CELL_RUN_GUTTER}px; }`);
 	collector.addRule(`.notebookOverlay .cell-list-container > .monaco-list > .monaco-scrollable-element > .monaco-list-rows > .monaco-list-row  > div.cell.markdown { padding-left: ${CELL_RUN_GUTTER}px; }`);
 	collector.addRule(`.notebookOverlay .cell .run-button-container { width: ${CELL_RUN_GUTTER}px; }`);
-	collector.addRule(`.notebookOverlay > .cell-list-container > .cell-list-insertion-indicator { left: ${CELL_MARGIN + CELL_RUN_GUTTER}px; right: ${CELL_MARGIN}px; }`);
 	collector.addRule(`.notebookOverlay .cell-drag-image .cell-editor-container > div { padding: ${EDITOR_TOP_PADDING}px 16px ${EDITOR_BOTTOM_PADDING}px 16px; }`);
 	collector.addRule(`.notebookOverlay .monaco-list .monaco-list-row .cell-focus-indicator-top { height: ${EDITOR_TOP_MARGIN}px; }`);
 	collector.addRule(`.notebookOverlay .monaco-list .monaco-list-row .cell-focus-indicator-side { bottom: ${BOTTOM_CELL_TOOLBAR_HEIGHT}px; width: ${CELL_MARGIN + CELL_RUN_GUTTER}px; }`);