As already pointed out by Ronald. We have a feature for building adn exposing your own Microflow actions. You can build custom Java actions and expose them as your own Microflow action.
* How-to about the creation of a custom MF action
* You can ship these MF actions to the App store too (AWS IoT example)
* When you provide category, icon, name, the action is also available from the Microflow toolbox. Shown as first class microflow action.
As you notice it is not completely clear what kind of customisation you expect. As Ronald pointed out you can add custom java actions and you can also expose them in your project:
I am not sure what you mean here. Every Mendix model can be adapted with custom microflows to perform actions.
You can only extend actions with connectors or custom Java actions. Those will show up in the list of actions.
We cannot add any new activities that can be added in to Mx modeler. We can only use all the available activities from the modeler.
For creating custom microflow actions you can do like this.Create java action inside the java action properties check the checkbox for expose as microflow action and run in ecilipse.