src/vs/platform/userDataSync/common/ignoredExtensions.ts/IgnoredExtensionsManagementService/updateIgnoredExtensions
class IgnoredExtensionsManagementService:	updateIgnoredExtensions(ignoredExtensionId: string, ignore: boolean): Promise<void> {
		// first remove the extension completely from ignored extensions
		let currentValue = [...this.configurationService.getValue<string[]>('settingsSync.ignoredExtensions')].map(id => id.toLowerCase());
		currentValue = currentValue.filter(v => v !== ignoredExtensionId && v !== `-${ignoredExtensionId}`);

		// Add only if ignored
		if (ignore) {
			currentValue.push(ignoredExtensionId.toLowerCase());
		}

		return this.configurationService.updateValue('settingsSync.ignoredExtensions', currentValue.length ? currentValue : undefined, ConfigurationTarget.USER);
	}