Re: Old QB a mess. Started over 1/1 with new QB online without importing anything. Checking reconciliation off by the checks written in 2018 but cashed in 2019. Journal?
Journal entries should be the exception when using QB, they often do not work as you think they should, and when you use inventory type items they never work for inventory. It is much better to use the forms on the home page the way QB is designed to be used. Journal entries also bypass accrual/cash reporting, and will not show on many reports.
Open checks that were out in the wild when you started the books, need to be entered, and after entering the old checks, adjust the entry you used for a starting balance down to account for those values. Then you can recon the bank account