Hi @touma 
I want to note that your suggestions are indeed interesting.
We have registered proposals for two out of three of your suggestions:
Document Editor:
1. Implement the ability to quickly jump to the cursor or cell of users in co-editing mode.
Smooth scrolling
Spreadsheet Editor:
3. Decrease the scroll step when scrolling through the table.
Please provide more details on the second suggestion for better understanding of the concept behind your proposal.
If possible, provide examples of the issue you encountered.