Warning

Some APIs might get changed in the future

You can use AbsRenderer to control how each field is rendered.

Example type:

public class MyMonoWithCustom : MonoBehaviour
{
    public string myString;

    public bool toggle;
    public string input;

    public int myInt;
}

Now let's make a toggleable input

using SaintsField.Editor.Playa;
using SaintsField.Editor.Playa.Renderer.BaseRenderer;
using UnityEditor;
using UnityEngine.UIElements;

[CustomEditor(typeof(MyMonoWithCustom), true)]
public class MyMonoWithCustomEditor : SaintsField.Editor.SaintsEditor
{
    public override IEnumerable<AbsRenderer> MakeRenderer(SerializedObject so, SaintsFieldWithInfo fieldWithInfo)
    {
        if (fieldWithInfo.FieldInfo != null && fieldWithInfo.FieldInfo.Name == "toggle")
        {
            yield break;  // returns nothing to show nothing
        }

        if (fieldWithInfo.FieldInfo != null && fieldWithInfo.FieldInfo.Name == "input")
        {
            yield return new ToggleInputRenderer(so, fieldWithInfo);  // custom rendering
            yield break;
        }

        // default rendering
        foreach (AbsRenderer defaultRenderer in base.MakeRenderer(so, fieldWithInfo))
        {
            yield return defaultRenderer;
        }
    }
}

public class ToggleInputRenderer: AbsRenderer
{
    private readonly SerializedObject _serializedObject;
    public ToggleInputRenderer(SerializedObject serializedObject, SaintsFieldWithInfo fieldWithInfo) : base(serializedObject, fieldWithInfo)
    {
        _serializedObject = serializedObject;
    }

    public override void OnDestroy()
    {
    }

    public override void OnSearchField(string searchString)
    {
    }

    protected override void RenderTargetIMGUI(float width, PreCheckResult preCheckResult)
    {
    }

    protected override float GetFieldHeightIMGUI(float width, PreCheckResult preCheckResult)
    {
        return 0;
    }

    protected override void RenderPositionTargetIMGUI(Rect position, PreCheckResult preCheckResult)
    {
    }

    protected override (VisualElement target, bool needUpdate) CreateTargetUIToolkit(VisualElement container)
    {
        VisualElement root = new VisualElement
        {
            style =
            {
                flexDirection = FlexDirection.Row,
            },
        };

        Toggle toggle = new Toggle("Input")
        {
            bindingPath = _serializedObject.FindProperty("toggle").propertyPath,
        };
        toggle.AddToClassList(Toggle.alignedFieldUssClassName);
        root.Add(toggle);

        TextField input = new TextField
        {
            bindingPath = _serializedObject.FindProperty("input").propertyPath,
            style =
            {
                flexGrow = 1,
                flexShrink = 1,
            },
        };
        root.Add(input);

        return (root, true);
    }

    protected override PreCheckResult OnUpdateUIToolKit(VisualElement root)
    {
        // If needUpdate=true, this function is called every 0.1s. You can do some ticking update here.
        TextField textField = root.Q<TextField>();
        textField.SetEnabled(_serializedObject.FindProperty("toggle").boolValue);

        // return the required value
        return base.OnUpdateUIToolKit(root);
    }
}