Is there some way to write a csv file such that , when opened in MS Excel , it will open in different tabs in the workspace ?
The short answer is, NO.
For that matter, the long answer is NO too.
csv is a continuous run of lines of values separated by commas. each line doesn’t even have to have the same number of values etc. there’s no concept of workbooks or different “areas” in csv. Excel cannot be cajoled into opening a csv into multiple workbooks…well at least not without writing VBA to parse the csv file yourself.
the oxml or whatever they’ve ended up calling the xml file spec for office, allows workbooks and is still easy to deal with being text based. Do you have to use csv or can you switch (at least part way through) to xml?