My son and I put some cash together which he used to purchase some ADA currency for the both of us, under his account. Subsequent to that, after I had set up my own trading accounts and my Yoroi wallet, he transferred my share of the ADA coins to my Yoroi wallet.
How do I now account for this transaction from him to me?
Buying crypto isn’t taxable, so just leave it as if you purchased it yourself and add a deposit transaction into Koinly for the amount of ADA you received. Later on, when you go to sell that ADA you’ll realize gains on it and that will show up in the system.