f js

app/assets/javascripts/rails_admin/custom/grade-groups.js

@@ -24,13 +24,23 @@ $('[data-component="grade-groups"]').each(function () {
     newGroupOption.value = grades.join(',');
     newGroupOption.text = options.map(o => o.text).join(', ');
     groupSelect.appendChild(newGroupOption);
+    options.forEach(o => o.remove());
   });
 
   $('button[data-action="move-to-grades"]').on('click', function () {
     const options = Array.from(groupSelect.selectedOptions);
     const groups = options.map(o => o.value.split(',').map(grade => parseInt(grade)));
+    const texts = options.map(o => o.text.split(','));
     const newValue = value.filter(a => !groups.some(b => arrayEq(a, b)));
     setValue(newValue);
     options.forEach(o => o.remove());
+    groups.forEach((grades, i) => {
+      grades.forEach((grade, j) => {
+        const newGradeOption = document.createElement('option');
+        newGradeOption.value = grade;
+        newGradeOption.text = texts[i][j];
+        gradeSelect.appendChild(newGradeOption);
+      });
+    });
   });
 });