Define Fields inside Editable Grid in Form of Model-Driven-App as required via JavaScript

I would like to define several columns in multiple editable grids in the same form of my model-driven-app as required. The sense behind this is that we have 2 different model-driven-apps for 2 different user-roles and for one specific role some fields should be required.

To reach this goal I would like to use the JavaScript approach via a webresource.

My first approach trying to avoid JavaScript unfortuantely does not work.
I already tried to solve this via Power Automate flow and business rules but unfortunately this would cause a conflict because the business rule triggers too fast

In attachment my code which is unfortunately not working. I am still having problems to access the attribute in my editable grid. I have uploaded the function as webresource and embedded the webresource in the OnLoad-Event of the respective Form of the model-driven-app.

The following error is returned: repairActivityGridEntity.getEntityMetadata is not a function

Code:

function setRequiredFields(executionContext) {
    let formContext = executionContext.getFormContext();
    let repairActivityGridContext = formContext.getControl("RepairActivitys");
    let repairActivityGrid = repairActivityGridContext.getGrid();
    let repairActivityGridRows = repairActivityGrid.getRows();
    if (repairActivityGridRows.getLength() > 0) {
      let repairActivityGridData = repairActivityGridRows.get(0).getData();
      let repairActivityGridEntity = repairActivityGridData.getEntity();
      let repairActivityGridEntityMetadata = repairActivityGridEntity.getEntityMetadata();
      let repairActivityGridColumns = repairActivityGridEntityMetadata.Attributes;
      for (let i = 0; i < repairActivityGridColumns.getLength(); i++) {
        if (repairActivityGridColumns.get(i).LogicalName == "mca_overnightstaysindays") {
          repairActivityGridColumns.get(i).RequiredLevel = "required";
          break;
        }
      }
    }
    repairActivityGridContext.addOnLoad(setRequiredFields);
  }

I tried to solve it with JavaScript but it does not seem like that I could solve it to access an attribute in an editable grid on the OnLoad-event of my form. Maybe someone know how to achieve this/ what I am doing wrong.