Submit self-assessment via FreeAgent, then send Capital Gains Tax form SA108 separately?

I use FreeAgent to send my self-employed self-assessment. It does all the calculations for me and uploads to HMRC. However, it doesn't support Capital Gains Tax and I owe about £500 in CGT from selling shares inside a General Account this year. Can I submit my self-assessment via FreeAgent, then somehow supplement this with Capital Gains Tax calculations after? Like sending the CGT SA108 paper form after? I really don't want to have to abandon the accuracy of using FreeAgent just because I have a small amount of Capital Gains Tax to pay.

Hi,
No, the whole return should be submitted together at the same time.
Thank you