Is there a way to plot all my past trades from an excel given by MT4 into a chart in MT4 to see exactly where I opened and closed my positions
By learning MQL or by opening a job in freelance section.
I said it was possible, not that it would be easy, but it's certainly do-able and a good project for starters.
If you just want to visualise certain trades, and there aren't too many, you can drag a trade from the Account History tab on to the relevant chart, and it will show you the start and finish of the trade. Obviously if there are lots of trades this may become tedious, but it's something you could do straight away with no coding etc. Hope that may help.