Unity Custom caret, set caret position from world position, from raycast. A script for Unity3D to customize the caret of a Text Mesh Pro Input Field game object.

CustomUICaret.cs

using TMPro;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using UnityEngine.Scripting;

/// Should be Used in combination with the Second Transparent text ( substring of the inputfield text based on inputfield caret position)
/// This transparent text should use ContentSizeFitter + Horizontal Layout Group. Add Text Caret as child to the transparent text.
/// This way you will always have the same alighment as the original text.
/// Be sure to use Update function to set custom transparent text acording to new InputField caret Position (update function)
/// Add Separate Event Trigger with some UI Image Element On Top Of the Input Field. 
/// Make sure anchors are the same for it as well as InputField Text.
/// Invoke OnClickMovePointerByEvenData from OnClick event
public class CustomUICaret : MonoBehaviour
    {
        [SerializeField] private TMP_InputField _inputField;

        public static Vector2 SetX(Vector2 vector, float value)
        {
            return new Vector2(value, vector.y);
        }

        public static Vector2 SetY(Vector2 vector, float value)
        {
            return new Vector2(vector.x, value);
        }

        public static Vector2 GetSize(RectTransform trans)
        {
            return trans.rect.size;
        }

        public static Vector2 GetPixelFromWorldPoint(RectTransform rectTransform, Vector3 worldPoint)
        {
            Vector3[] v = new Vector3[4];
            rectTransform.GetWorldCorners(v);
            var loverLeft = v[0];
            var upperLeft = v[1];
            var upperRight = v[2];
            var worldDistanceWidth = (upperLeft - upperRight).magnitude;
            var worldDistanceHeight = (upperLeft - loverLeft).magnitude;
            Vector2 imagePos = Vector2.one * -1;
            var size = GetSize(rectTransform);

            // Assume lover left is (0,0) pixel
            // Project on worldHeight
            var vectorToWorldPoint = loverLeft - worldPoint;
            var upperLeftPosition = upperLeft;
            var projectOnHeight = Vector3.Project(
                vectorToWorldPoint,
                loverLeft - upperLeftPosition
            );
            // Project on worldWidth
            var projectOnWidth = Vector3.Project(
                vectorToWorldPoint,
                upperLeftPosition - upperRight
            );
            // if using sqrt - we will not know if it is inside
            var percentWidth = projectOnWidth.magnitude / worldDistanceWidth;
            var percentHeight = projectOnHeight.magnitude / worldDistanceHeight;

            if (percentWidth >= 0 && percentWidth <= 1)
            {
                imagePos = SetX(imagePos,percentWidth * size.x);
            }

            if (percentHeight >= 0 && percentHeight <= 1)
            {
                imagePos = SetY(imagePos,percentHeight * size.y);
            }

            return imagePos;
        }

        /// Invoke this method from OnClick on the event trigger
        [Preserve]
        public void OnClickMovePointerByEvenData(BaseEventData eventData)
        {
            // Get World Point
            var asPointerEventData = eventData as PointerEventData;
            if (asPointerEventData == null)
            {
                return;
            }

            // Transform Into Local Anchored Position
            var positionWorld = asPointerEventData.pointerCurrentRaycast.worldPosition;
            var fromExtension = GetPixelFromWorldPoint(_inputField.textViewport, positionWorld);

                       // find nearest
            float currentX = 0;
            int maxNumber = _inputField.text.Length;
            var TextObject = _inputField.textComponent;

            float constantValue = 0;
            for (int i = 0; i < maxNumber; i++)
            {
                if (i == 1)
                {
                    constantValue = TextObject.textInfo.characterInfo[i].xAdvance;
                }

                if (currentX >= fromExtension.x)
                {
                    _inputField.caretPosition = Mathf.Clamp(i - 1, 0, maxNumber);
                    return;
                }

                if (TextObject.textInfo.characterInfo.Length > i)
                {
                    currentX = TextObject.textInfo.characterInfo[i].xAdvance;
                }
                else
                {
                    currentX += constantValue;
                }
            }

            _inputField.caretPosition = maxNumber;
        }
    }

this will set your caret into target world position ( raycast position)