https://github.com/egh/ledger-autosync has been real handy for me with transactions.

My "entry" work is modifying some categories that it gets wrong.

I don't fully understand your situation, so I'm not expecting it necessarily solve your entry problems. I'm only raising awareness.

I agree that entering large numbers of manual transaction can be clunky, but for the occasional single transaction it can be pretty quick. For larger numbers of transactions, I've created a rules file that hledger uses to parse the downloaded CSV file from my bank to create a fairly detailed journal entry. (https://github.com/simonmichael/hledger/wiki/Convert%20CSV%2...). The real added benefit for me is using git not only for my journal file, but also for the CSV files. It gives me an immutable record of transactions from my bank. I had a revelatory experience reading adept's methods for tracking his financials. Version control for everything. https://github.com/adept/full-fledged-hledger

Ledger can import GnuCash databases, so in theory you could do the the insertion in GC and processing in Ledger :)

Instead of GnuCash, I use KMyMoney. It saves everything in XML.

To use Ledger, I essentially use KMyMoney for entering transactions, and wrote a Python script to convert the XML into a file Ledger can read.

You may want to see if that's possible with GnuCash?

I believe I remember seeing some CSV to Ledger-cli tools if you can get the data into that format.