The wonderful Rob Wunderlich provides an excellent way to annotate QlikView charts with event related data in his post at https://qlikviewcookbook.com/list-recipes/#squelch-taas-accordion-shortcode-content-40 - kudos as always !
The detailed steps are not available in Sense charts.
A wizard-driven feature in Qlik Sense to achieve a generic solution would be a value add. So many date based charts would gain value from a simple mechanism to overlay the chart and its data points with event annotations. Imagine a sales bar chart getting enhanced with key marketing campaign data labels, HR salary chart getting enhanced with key recruitment events, a financial chart getting enhanced with key economic events, etc etc. So many use cases.
Finally if provided via a wizard entry this opens up Sense for business analysts to really help drive more collaboration and value-add adoption of the product. Charts by themselves do not always answer the "why" question.
Longer term, future dated events still to happen could maybe integrate with Ping alerting.