EnumFlags as buttons but in custom editor window

Hi there, I’m using an asset called enumFlagsAsButtons (Enum Flags as Buttons | Utilities Tools | Unity Asset Store) that is super helpful for my game. It turns enumFlags into buttons I can just tap (and my game has a lot of them) so it makes life easier for me.

Problem:
I am in the process of making a custom editor window, but I don’t know how to get the enumFlags to display as buttons in this new window. My code so far:

using UnityEngine;
using UnityEditor;

[System.Serializable]
public class WordMaker : EditorWindow
{
    string englishWord;

    [SerializeField, EnumFlags]
    public Categories categories;

    [MenuItem("Window/WordMaker")]
    public static void ShowWindow()
    {
        GetWindow<WordMaker>("Make a word");
    }

    private void OnGUI()
    {
        GUILayout.Label("Enter words here", EditorStyles.boldLabel);

        englishWord = EditorGUILayout.TextField("English Word: ", "");

        categories = (Categories)EditorGUILayout.EnumFlagsField(categories); 
    }
}

I contacted the maker of the asset and he says my line:
(Categories)EditorGUILayout.EnumFlagsField(categories);
is telling Unity to use the drop down enum flags property but he said he couldn’t help me much beyond that as it had been so long since he’d used it… So here I am.

Normally, in the inspector, you just add the [EnumFlags] attribute above the enum variable and it will make them selectable buttons. I can’t paste his script here for obvious reasons (a paid asset).

Question:
How can I display the enumFlags as buttons in a custom editor window?

Thanks in advance.

Bump. Anyone?