First, let me say that Checkbook exceeds my expectations. The first 4 or 5 things I was going to request are already in the program. Good job!
It may be that some of my requests below are also built-in and that I just haven't figured them out yet.
Here is my list in order of priority.
#1. Tie Description to To/From. I have explained this in a separate post
#2. Button to DUPLICATE an existing entry so only have to change a few items like perhaps date and amount.
#3. Either a new, narrow column or some indicator (maybe a color or an asterisk) to identify that an entry came from SCHEDULED list. A column would be preferred because then one could make a Summary Report that totals the monthly scheduled payments, or the yearly scheduled payments, etc.
#4. One or 2 new "category" columns, explained in a separate post and illustrated by an example in #3. Maybe 3 or 4 new "category" columns because the more I reflect on this, the more uses I find for useful summaries. The Summary design in Checkbook is very, very good and can be even more powerful if users had a few new columns to play with.
#5. Ability to import and export from/to spreadsheets or CSV. I would like to have been able to import my Excel spreadsheet when I started up, but I couldn't figure out a way. (Too late for me now because I manually entered what was needed.)
#6. Instead of just a check box for tax-free, I would like to be able to enter an amount. I have several payments that are partially tax-free and I don't see a way to use Checkbook in its current form to track these.