Currently, when importing from Excel, cell Notes are converted to Cell Messages, but Cell Messages don’t show up when hovering over the cell.
Cell Notes in Google Sheets (the black triangles) and Excel (red triangles) are extremely useful as help text in templates for explanation of inputs, column labels, and outputs.
Although I can use Cell Messages in spreadsheet.com for now, to function as help text, the text needs to pop up when hovering over the cell. The added steps of having to right-click and select Cell Messages just to see help text is not a great user experience.
Google Sheets lets you have both a Note and Comments within a single cell, but Excel disables comments if the cell has a Note. Google Sheets incorrectly imports cell Notes as Comments, so even Google Sheets is still having problems.
If you’d like to innovate, then you could introduce the concept of custom Help Text for a cell. This might show up as a very small blue circle or triangle in the upper left corner of the cell. Then, when hovering over the cell, or selecting the cell, the blue circle could expand into a larger blue circle with a question mark which when hovered over or clicked would display the help text. If you were exporting to Excel or Google Sheets, you could have the help text convert to a Note instead. And maybe when importing from Excel or Google Sheets, a Note could be imported as Help Text.