@Corleone ,
Combo Boxes with multiple selections will only show the number of items when selected and nothing in view mode as the selections are actually a table. I would suggest the following. Change all names below with Your to your actual names.
Unlock the card and put a Label on it with the Text
Concat(YourComboBoxName.SelectedItems,Value & ", ")
I am assuming your field is a Choice type with the Value reference above.
Now make the Visible of the Label
YourFormName.Mode = FormMode.View
Lastly, the Visible of the ComboBox
!YourLabelName.Visible
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