An hour to six days is bad. There must be some kind of data ingestion and pipeline involved. Reading a database and generating a formatted xlsx file can be a few seconds to minutes.
An OpenXML library could modify and write to a new file without Excel. Microsoft’s version is usually for C#, there are similar libraries in other programming languages if your computer is locked down. If Excel gives a corrupted error when opening, the XML data can be viewed by renaming the xlsx extension to zip.
An hour to six days is bad. There must be some kind of data ingestion and pipeline involved. Reading a database and generating a formatted xlsx file can be a few seconds to minutes.
An OpenXML library could modify and write to a new file without Excel. Microsoft’s version is usually for C#, there are similar libraries in other programming languages if your computer is locked down. If Excel gives a corrupted error when opening, the XML data can be viewed by renaming the xlsx extension to zip.
Merging Cells: https://learn.microsoft.com/en-us/dotnet/api/documentformat.openxml.spreadsheet.mergecells?view=openxml-3.0.1
Cell style and background color: https://stackoverflow.com/questions/44839512/how-to-work-with-style-index-in-open-xml