Momentum (M) Indicator:

This is a simple indicator where the indicator looks at the Momentum (M) value of all the candles.  Starting with the latest formed candle, the indicator compares its M value with the previous formed candle.  If the M value of the latest formed candle is higher than previous candle it places an upward pointing arrow (up arrow) below the bottom wick (BW) of the candle and if it is lower than previous candle’s M value, it places a downward pointing arrow (down arrow) above the top wick (TW) of the latest candle.  It should place arrows for all candles in all time frames (TF) by comparing their M values with the M value of their previous candles.   

I am giving you an example of a previously designed indicator by another developer.  This is another indicator (called BSR indicator), this is NOT M indicator.  I am simply showing you this as an example.  The arrows for the M indicator should also look like this BSR indicator.  I have attached here the ex4 file of this indicator and you can place it on an MT4 chart for you to see how it places arrows above and below all the candles.  
I have attached a screenshot of a eurusd pair’s D1 chart where this indicator placed the arrows.  The M indicator that you will be designing should place arrows in the same way above and below all the candles.  

In order to get the M values for candles, place Momentum (M) Indicator on the bottom of your chart.  This is a standard indicator on MT4 platform.  After placing the indicator on your chart, place your cursor on an already formed latest candle, then the indicator will show the M value in the Data Window.  

For your information, these are the M values of different D1 candles of different days on a eurusd currency pair:

July 8 2022: 96.8972
July 7 2022: 96.8487
July 6 2022: 96.5171
July 5, 2022: 98.2634

Now to get the arrow of the latest formed candle of July 8, the indicator compares the previous candle of July 7 M value with July 8 value.  July 8 value is larger than July 7 value.  Hence July 8 candle gets an up arrow placed under its BW.  Now, to get the arrow of July 7 candle, indicator compare its M value with July 6 candle’s M value.  July 7 value is larger than July 6 value.  Hence July 7 candle also receives an up arrow placed under its BW.  Now to get the arrow of July 6 candle, the indicator compares July 5 candle M value with July 6 candle’s M value.  July 6 value is smaller than July 5 candle value.  Hence July 6 candle receives a down arrow placed above its TW.  Likewise, every candle receives either an up arrow or a down arrow either below or above it, by comparing its M value with its previous candle’s M value.  All the formed candles of all time frames should have these arrows placed either below or above them with a visualization setting, so that we can place them selectively only in some TFs if we choose to.  The default setting should be arrows placed in all TFs.  

If there are any questions, please contact me ASAP.  This is a very simple indicator with very simple and clear logic.  It is important that you understand it clearly before designing it.  I can help you understand the logic if there are any questions on it.