I don’t think you can call a microflow on tab change. When I needed to do something similar in the past, I used a series of microflow buttons styled to look like tabs.
Not support from the core widgets. Mike’s suggestion would be a good, to style buttons like a tab.
On other creative way, it to have a data view with a data source microflow in the tab. Set the tab the property “Refresh on show” this might trigger more often than you want….
If you are into widgets, you might be be able to extend this widget. https://appstore.home.mendix.com/link/app/894/. I am willing to accepting a good pull requests. https://github.com/Andries-Smit/TabExtension and publish it.