It is currently possible to transfer cash from your Freetrade GIA to your ISA (by contacting support, and in the future this will be a function in the app).
Other platforms implement effective transfer of shares with “Bed & ISA”. You call them up, and then they sell the shares in your GIA and immediately buy them back in your ISA. The idea is you won’t lose much if the share price is fluctuating.
If they charge for trades, they typically only charge you once, eg. for the sell.
Would be great if Freetrade implemented something similar, but without the requirement to call them (or use in-app support), and by charging the instant trade fee only once, so £1 for the whole operation.