Could anyone advise if there is a tool or method through FI which allows you to record a snapshot of your portfolio at a future or historical point?
Nothing built into FI. You could for historical snap shots use screen shot on your phone. Snap shots of your future protfolio I'm still working that one out ;-)
@Timelord should be able to assist here if he is still trading, although he may be back in 2134 this week