Just looked at this widget in the appstore: https://appstore.home.mendix.com/link/app/2790/ and then looked at https://v4-alpha.getbootstrap.com/components/input-group/ because custom widgets (especially from 3rd parties) are always a risk in the future for maintaining the project. And I noticed that the Input Group Addon from Bootstrap really is a tiny bit of HTML with a class, so easily added.
Now adding a container, two spans and classes all over your pages is quite some work to maintain. Would be great if Mendix would support the basics (textual before and after addon) as setting on each input-widget that comes as standard with the modeler.
Just wanted to bump this idea. We often use the bootstrap input addon widget, but as Jelle mentions, it is a risk for maintaining the project.
I would love to see these input addons as default functionality in Mendix