Hello again.
I am not sure that I made the problem clear enough. It is not a matter of technical implementation. The stakes cannot be assigned to users. A stake amount is dependent on the total staked balance amount, not the balances of individual users. There is no 1-to-1 mapping of address balances and user balances. Hence the need for an investment plugin extension, which I have not yet developed.
Deposit transactions are normally discovered by the coin adapters and are transmitted into a handler Dashed_Slug_Wallets_TXs->action_wallets_transaction() via the wallets_transaction action. But this will not help you insert stake rewards into the DB.
hope this is a bit more clear