Yes, you can add many different data sources to dashboards. Just add a new data source. Make sure you map the fields that exist across both surveys to existing fields - e.g. geography, etc. - that you can use as filters or widget attributes. And then just map the new survey questions as additional fields.

Hi InessaG,
Thanks for our advice, may I further enquire whether both the data sauces added would be shown onto the same chart or in different charts of the dashboard?
In addition, would you know on any online guide on the question above that could be referred to for my better understanding on the steps?

Regards
Doris

You should be able to display on the same chart. I do it on my end - for example, I'm measuring customer effort score across various customer journeys through different surveys, and display those scores in one widget - in my case, these score questions are mapped to the same field, but you can play around with what you need to show.
You can always go on support.qualtrics.com and search for the topic of interest. If you search for data source, you get this: https://www.qualtrics.com/support/vocalize/getting-started-vocalize/pages-overview/