I don’t believe this is possible, can’t easily see it as an option.
I have transferred my existing ISA into Freetrade. The issue is on the portfolio valuation it just shows the a 0.00% change. It doesn’t even show the change in value since the shares came into the Freetrade portfolio. It would be fantastic if you could put the historical cost that you purchased these shares at, such that then you could see the percentage change from the original share price.