if you want to link an IDE with Mendix, you can use Eclipse IDE, and then you will be able to see the Source code and make Java actions.
To do so, open Studio Pro and then, on the top menu, click on ‘App’ and then click deploy for eclipse,
Now, open Eclipse, and then, you can import the Mendix project by browsing to the directory.
Let me know, if you face any issues,
Hope it helps!!
You can use Eclipse to write and debug Java actions in your Mendix app.
Refer the below link for setting up Eclipse for the project
Hope it helps!!!
As per you explanation in the comment you can do the below.
First you need a code execution engine. For e.g.: Judge0 is 1 such service which you can use to execute code.
This service give you REST APIs.
So in the mendix app, to start with you make a simple page in which there should be a simple input-box or a text-area to write the code. Then on submit of this page you can call the Judge0 APIs to get back the Code Errors or Output.
Let me know if you got the points :)