delete all transactions from prior year, retaining balance

I don't think there is a perfect solution for what you're asking. I've tried experimenting a little and here's what I'm coming up with, but maybe others will have a better idea. I've used HomeBank for a couple of years, and I'm no expert.

Method 1. Make a copy of your .xhb file and name it 2020, and make another copy and call it 2021. You'll need to take care and record balances as you begin to edit each file. When you delete everything from 2019 and earlier in your 2020 file, you will need to add a "dummy transaction" (credit or debit) to get your 2020 initial balance correct. Deleting all your 2021 data from this file will not change the balance, so it should give you what you want. But you will again need to take care with your 2021 file when you delete everything from 2020 and earlier, and you'll again need a "dummy transaction" to get your initial balance correct. This will maintain all of your payees, memos, and so on, because it is all based from the same source file that you have been using.

If you start a brand new file for 2021, it will start at a $0.00 balance, so you'll need a deposit to bring it to your initial balance for the year. But you'll lose your payees, memos, etc. Creating a new file has an option to include many pre-made categories, so if you used those they would come back to you, I think, but any custom categories would be lost.

Method 2. (This is what I do.) I have 2 years of data now, and I'm also getting ready for taxes. I open my Checking register, and then using the Range selection (upper left) I choose Last Year. Then clicking the Account Menu (far upper left) I choose Export CSV. I can then open the .csv file with LibreOffice or Excel and format the information that I want to keep for tax purposes. The .csv file does not save the balances of the checking account, but that shouldn't be needed for taxes. If you choose Export as PDF instead of CSV, that will show the balances, but you can't edit it. You may need to repeat this for Savings accounts, CD's, or other accounts you may need to total your taxable income and your deductions. Even if you create multiple files, you can copy/paste them together in a single CSV with a nice printable format that you would create yourself.

Besides opening each account like described above, you can also use the Reports (>Statistics) menu to sort and save to a CSV file. With the Statistics Report menu, you can set the Date Filter to Last Year, and then choosing View By as Payee (or Category, or Subcategory), and Type as Income, Expense, or Total to show both. This report when saved as a CSV does not show the date of each individual transaction, but individual dates are probably not needed for taxes either.

Sorry this is so long. I hope that it helps to get you started. HomeBank's filtering ability is very helpful to get ready for taxes, but it takes some getting used to. I plan to keep the same data file going forward for many years... this will show better long-term analysis of income and expenses, I think, and the filters will let me separate the data as needed.

One last caution... watch for Transfers between accounts, or any other relationships between accounts. If you try to isolate one year from the next, you may break/lose relationship links. I did not experience this, but it seems like something that could happen.

Good luck!
Stan