extensions/markdown-language-features/src/preview/previewManager.ts/MarkdownPreviewManager/toggleLock
class MarkdownPreviewManager:	public toggleLock() {
		const preview = this._activePreview;
		if (preview instanceof DynamicMarkdownPreview) {
			preview.toggleLock();

			// Close any previews that are now redundant, such as having two dynamic previews in the same editor group
			for (const otherPreview of this._dynamicPreviews) {
				if (otherPreview !== preview && preview.matches(otherPreview)) {
					otherPreview.dispose();
				}
			}
		}
	}