We have two objects, mentors and students. When we click on the save button when we've filled in student info, we want to get a microflow work which compute automatically the new fillrate (number of students / capacity) of a mentor and automatically determine which mentor is available for the next time we fill in student info and assign a mentor to this student. But then the trouble starts. When we make our own 'save-button' and want to call that microflow, we get the message that 'selected microflow should have one parameter of type MyFirstModel.Student'. The only solution we could think about is that we create a microflow button at the mentor form which calls the selected microflow, but we want the computation to do automatically when create/edit some studentinfo.
In the microflow triggered by the custom save button on the student form you could try and retrieve the mentor information (probably from the database). From the mentor data you could find the mentor that has capacity left and link the student (or whatever you need, that's not completely clear from the description).