Importing variants, tags, etc.often requires to format the structured file before importing it. Unfortunately, Odoo only allows values separated by commas. So it could be painful to reformat the file with the aim to concatenate each value in a single cell.

The solution is the "M2M Concatenator" tool available by creating this following Gspreadsheet : 

Under the Script menu, you will find two modes of concatenation handled by GScript.

Single ID Mode

This mode works if your file contains one ID per group of lines, for example :

ID	Value
1	A
	B
2	X
	Y
	Z

Using this mode will generate the following table :

ID	Value	Concatenation
1	A	A,B
	B
2	X	X,Y,Z
	Y
	Z

Duplicated ID Mode

This mode works if your file contains one ID per line even if multiple lines are related to the same ID, for example :

ID	Value
1	A
1	B
2	X
2	Y
2	Z

Using this mode will generate the following table :

ID	Value	Concatenation
1	A	A,B
1	B
2	X	X,Y,Z
2	Y
2	Z

Instructions to use
1. Make a copy of the sheet in your own Google Drive.
2. The GSheet has to contain at least the following columns : id & value.
3. Depending on the structure of your file, run the right concatenation mode described above.
4. The script will create the column "Concatenation" with the concatenated values.
5. Note that the concatenation automatically removes the duplicated values and this system is not case sensitive. It means that if, for the same ID, the column "Value" contains "Red" and "red", the "Concatenation" column will only contain "Red".
6. Save the GSheet as Excel or CSV.
7. Remove the lines without concatenation by sorting on it.
8. Import your file in Odoo.