This doesn’t look like a normal transpose. Do you want to rearrange your data by cell color? Or do you want to group the data in Column 2 based on the elements in Column 1? In the latter case I suggest using the GroupBy node with Column 1 as grouping column, and group the elements of Column 2 together as a List. Then, use the Expand Split Collection Column node to expand sideways. Then, apply Transpose node.

Thank you Aswin. I actually put the colors, in thinking it would help for the understanding !
What node should I use to group the elements of column 2 together, knowing that the numbers of the second columns are linked to the numbers of the first column?
For instance, 7 & 6 from column 2 are linked to 5 from the first column. Hence the reason why when I transpose, 7 & 6 should be below 5 (see column 3 of the second chart). Not sure if I am clear. Please let me know otherwise…

(A bit annoying that I had to resort to a Java Snippet to create an empty column of type Int. Are there better ways to do this? Ideally the Constant Value Column would contain an “empty column” option) KNIME_project3.knwf (28.8 KB)

Column Expression node creates empty column of type Int with missingValue() function and column type as Integer chosen. Rule Engine node without any rules creates an empty column but type String. To get type Int add rule FALSE => 1 (or any other number) i.e. some rule which will never be true but if would be true would have integer value. The latter is a bit weird but can do the job

Not sure Constant Value Column would be a best place to add this option but seems like an idea worth thinking about

…or a Math Formula with 0/0 as the expression. This yields NaN, and when one checks the “Convert to Int” box, the NaNs are converted to an empty column of type Int. (Edit: it turns out that also Double NaNs are converted to to an empty column, albeit a Double column)

Still, I think an “empty column” checkbox in the Constant Value Column node or a dedicated Empty Column node would be more elegant

Thank again both of you for the effort!
I however notice that the Groupby node does not work when you have a repetition in the second column. For instance, with the below set of data the flow does not work.

It looks the same from the outside, but I made changes in the configuration of the Create Collection Column and the GroupBy nodes. Are you sure you are looking at the updated workflow and not the old one?