Just noting to anyone interested here, I wrote an unofficial Chrome Extension to do some of these things! Open to any suggestions and new issues: https://github.com/adamtaylor13/moneymover

Reviewing transactions should be like a keyboard-driven high-speed mini-game. Start at the top of the queue (user can filter / sort queue however they like), focus the first transaction, and let the user use single-key shortcuts to focus any given column they want to change, then type their input and press enter to submit that column's data. Once user is done with that entry, they can hit space or enter (which automatically sets the entry to complete) and the focus proceeds to the next entry. Use arrow keys to move focus up and down the queue. Press escape to exit any modal or column data entry.

I would shy away from relying solely on tab to change column focus - we might have 100s of entries to review and edit in a month, this can quickly become exhausting hitting tab and shift-tab to get to the needed column. Single-key shortcuts (e.g., c for category, n for notes) to jump directly to a column is critical for quick entry.

Also I strongly suggest making keyboard shortcuts an optional feature. Many users will hit them by accident and be confused, so maybe off by default and present an option to enable during initial setup.

Ok, it's ridiculous that the absolute minimum esc to get out (cancel) of a modal dialogue box doesn't exist. You're killing me Smalls. While you are in there fixing that oversight, please add enter/return to save/ok/default action out of those modal dialogue boxes.

Related: Allow for a simpler manual input process, making it possible for a complete keyboard and tab. I am not able to tab from the payee and category fields. I have to make the selection first, then tab.

A great example use-case IMO is Google Calendar. Being table to hit (T) to open "Today" and then use (M) or (W) to change the view to Month or Week is really great. Also you can use (N) to go to the "Next" month and (P) to go to the "Previous" month. It's especially nice around the end/beginning of the month as you're navigating back and forth to do reconcilliation.

another simple one would be to have esc automatically cancel a modal or dialog

This doesn't need to be shipped together...can start with some basic shortcuts for a new transaction, a new transfer, etc.

I would love love love to be able to categorize transactions via keyboard shortcuts. To me, being able to do that is far more important than having keyboard shortcuts elsewhere in the app. You could possibly split this into two items: "Keyboard Shortcuts for Categorizing Transaction" and then the general "Keyboard Shotcuts in LunchMoney."