FYI: This is a Community forum made up of mostly users like you and me. Comments directed toward the Quicken team should be made via Phone or Chat instead of in this forum.
Regarding your Citi card: Citi supports manual downloads for 2022 and 2023 YTD in QFX (or “Quicken”) format. You can select the appropriate date range in your online account and then download and save it to your hard drive. Then double click on that file and select Quicken to open it which will prompt Quicken to import the transactions in that file. The first time you do this for each account you should be prompted to select the account in Quicken to match the import to. This process is called the Web Connect (WC) connection method. Future WC downloads should be imported into the correct account without needing to select the account.
Unfortunately, Citi does not offer transactions downloads for any date prior to 2022. But for Dec 2021 you can download the statement from your Citi online account and then you can manually enter the transactions from that. (Citi does still offer statement downloads for 2021.)
If you have other non-Citi account(s) that you are looking to fill in transactions for the same time period: I suggest you log into you online account(s) and see if they offer WC manual downloading. If they do then you can follow the same process as noted above for Citi.
If they do not support the WC process, you have possibly two options available to:
Let me know if you have any questions.