Help needed to concatenate 11 cells on same sheet, all of them in
the same row into two. Of the 11 cells, only max of 2 in each row
are filled out, others are left blank. How can I concatenate these
11 cells into 2 for each row?

If I understand your question correctly, just link the with ampersands.
Assuming we are talking about the first 11 columns...

=A1&A2&A3&A4&A5&A6&A7&A8&A9&A10&A11

Well, the above formula is for concatenating the first 11 rows of a column,
which is not what you asked, was it? Try this formula assuming we are
talking about the first 11 columns (note, the technique is the same)...

=A1&B1&C1&D1&E1&F1&G1&H1&I1&J1&K1

Rick