Create a completely custom PAW control for KSP

CustomPartActionControl.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using UnityEngine;

namespace UINumericFloatEdit
{
    [KSPAddon(KSPAddon.Startup.FlightAndEditor, false)]
    public class CustomPartActionControlSpawner : MonoBehaviour
    {
        public static GameObject prefabsHolder;
        private static UIPartActionCustomFloatEdit prefab;
        private static FieldInfo fieldControlTypesInfo = typeof(UIPartActionController).GetField("fieldControlTypes", BindingFlags.Instance | BindingFlags.NonPublic);

        // this must run after UIPartActionController.Start()
        void Update()
        {
            if (prefabsHolder == null)
            {
                prefabsHolder = new GameObject("PartActionCustomPrefabs");
                DontDestroyOnLoad(prefabsHolder);
            }

            if (prefab == null)
            {
                foreach (UIPartActionFieldItem uiPartActionFieldItem in UIPartActionController.Instance.fieldPrefabs)
                {
                    if (uiPartActionFieldItem is UIPartActionFloatEdit stockComponentPrefab)
                    {
                        prefab = UIPartActionCustomFloatEdit.CreatePrefab(stockComponentPrefab);
                    }
                }
            }

            List<Type> fieldControlTypes = (List<Type>)fieldControlTypesInfo.GetValue(UIPartActionController.Instance);

            if (fieldControlTypes == null)
                return;

            UIPartActionController.Instance.fieldPrefabs.Add(prefab);
            fieldControlTypes.Add(typeof(UI_CustomFloatEdit));

            Destroy(this); // we're not needed anymore
        }
    }

    public class UI_CustomFloatEdit : UI_FloatEdit { }

    [UI_CustomFloatEdit]
    public class UIPartActionCustomFloatEdit : UIPartActionFloatEdit
    {
        public static UIPartActionCustomFloatEdit CreatePrefab(UIPartActionFloatEdit original)
        {
            GameObject prefab = Instantiate(original.gameObject);
            prefab.name = nameof(UIPartActionCustomFloatEdit);

            UIPartActionFloatEdit stockComponent = prefab.GetComponent<UIPartActionFloatEdit>();
            UIPartActionCustomFloatEdit modifiedComponent = prefab.AddComponent<UIPartActionCustomFloatEdit>();
            modifiedComponent.fieldName = stockComponent.fieldName;
            modifiedComponent.fieldValue = stockComponent.fieldValue;
            modifiedComponent.incLarge = stockComponent.incLarge;
            modifiedComponent.incSmall = stockComponent.incSmall;
            modifiedComponent.decLarge = stockComponent.decLarge;
            modifiedComponent.decSmall = stockComponent.decSmall;
            modifiedComponent.slider = stockComponent.slider;
            Destroy(stockComponent);

            prefab.transform.SetParent(CustomPartActionControlSpawner.prefabsHolder.transform);
            DontDestroyOnLoad(prefab); 

            return modifiedComponent;
        }
    }

    public class CustomFloatEditTestModule : PartModule
    {
        [KSPField(guiActive = true, guiActiveEditor = true, guiName = "custom floatEdit")]
        [UI_CustomFloatEdit(minValue = 0f, maxValue = 10f, incrementSmall = 0.5f, incrementLarge = 1f, sigFigs = 1)]
        public float modified = 5f;
    }
}