Cool! Looks promising!
Some UI/UX remarks...
- I would expect to find the 'new sheet' option near the sheet list (on top or on the bottom perhaps?).
- Creating a new sheet does not give an empty sheet (instead it presents the same info as in the preloaded example).
- How do you deal with different notations for numbers? Can I switch somewhere from #,###.## to #.###,##?
- Operators and currency is now displayed in gray, just like the comments. This hurts legibility more than it helps focus.
- When you can detect unit indicators, maybe allow users to click on them to change the unit to another (compatible variant). For example change kilometers to yards.
- Header and sub-header styles are quite similar, makes them hard to discern.