disable or remove enum entry from inspector

If you want to prevent the option from being selected from every script, you can go with the InspectorNameAttribute attribute.

 public enum MyEnum
 {
     MyEntry0,
     MyEntry1,
 
     // The name should be the "nice looking" name of the previous entry
     // So we can't use `nameof(MyEnum.MyEntry1)`
     [InspectorNameAttribute("My Entry 1")]
     MyEntry2,
     MyEntry3,
     MyEntry4
 }

If you want something a per-script solution, you'll need a custom attribute and property drawer

 using System.Collections.Generic;
 using UnityEngine;

 public class MyEnumFilterAttribute : PropertyAttribute
 {
     public int[] Values { get; private set; }
     public string[] Labels { get; private set; }
 
     public MyEnumFilterAttribute(params MyEnum[] ignoredValues)
     {
         List<int> values = new List<int>((int[]) System.Enum.GetValues(typeof(MyEnum)));
         List<string> labels = new List<string>(System.Enum.GetNames(typeof(MyEnum)));
 
         for (int i = ignoredValues.Length - 1 ; i >= 0 ; i--)
         {
             int index = values.IndexOf((int) ignoredValues[i]);
             values.RemoveAt(index);
             labels.RemoveAt(index);
         }
 
         Values = values.ToArray();
         Labels = labels.ToArray();
     }
 }

In an Editor folder

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEditor;
 
 [CustomPropertyDrawer(typeof(MyEnumFilterAttribute))]
 public class EnumFilterAttributeEditor : PropertyDrawer
 {
     public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
     {
         MyEnumFilterAttribute filterAttribute = ((MyEnumFilterAttribute) attribute);
         property.intValue = EditorGUI.IntPopup(position, label, property.intValue, System.Array.ConvertAll(filterAttribute.Labels, l => new GUIContent(l)), filterAttribute.Values);
     }
 }

 [MyEnumFilter(MyEnum.MyEntry0, MyEnum.MyEntry2)]
 public MyEnum myEnum;