TP and SL by clicking on the chart

Maybe I don't understand your question, but currently, you can look towards the left side of the chart to see an icon (once in a trade and you will have the option to move your TP or SL to a certain level. Both lines will also be visible. If you don't want to set the levels visually, you will also be able to set them by price and etc.

Williams Chris is correct that you can drag TP/SL, but this is only available with pending orders, also known as working orders in PTMC. And also if you set the TP/SL when you first open the position. If you open a position at the market rate without setting the TP/SL, you cannot modify the order at a later time to add a TP/SL. It's actually one of the more frustrating limitations of PTMC.

Rather than modify the open position to add TP/SL, you will create a pending/working order above and below the market price. If you are in a long position, you will set a sell limit as your TP, and a sell stop as your SL. Once these pending/working orders have been created, you can drag the orders around the chart for easy modification at a later time. Remember though, that once your TP or SL has been filled, you will need to manually cancel the other pending order as it will still be open. That is another one of the frustrating limitations of creating a TP/SL after opening a position.

I think the feature most folks are familiar with, which is also far easier to use in practice, is like the order creation functionality in M/T. You can right click anywhere on the chart to set a TP/SL for an open position. You can also add TP/SL to open positions without TP/SL, which is lacking from PTMC.

If I am mistaken and there is another method to modifying open position to add TP/SL, I welcome the correction. If not, this is a basic feature that should be included in ANY trading platform, even one as robust as PTMC.