It is possible to track Marketo form submission within Convert Experiences.
To do it follow the steps below.
In your Experiment Summary page go to your Goals:
Name the goal and save it:
Once it is saved, go to edit the goal and copy its ID:
Copy Code into Global Project JS
Replace the goal ID with your own:
Attach Goal to Experience
Attach this goal to the experience where you want to track submissions:
You are ready to go!