Creating a table or summary? Not sure how to describe it

Hi everyone,

I've attached a picture of what I need done. Long story short, we are transitioning from an old template to a new one, and so there are thousands of lines that need reformatting for the new software. I have a column, 1-10, marked by "x"s, and I wanted to create a "summary" column which gives a summary of what columns have "x"s in them for which rows. I know that sounds confusing, so let me explain via the attached image:

Column K shows that row 3 has an X for column data 5 & 8, therefore the output is 5 & 8.

So far I've been doing this by hand, but I realized there must be a more efficient way of doing so. Also, is there any way to have it ignore the grey shaded boxes? They are just summaries of the next few lines and will be deleted anyway.

Thank you all so much in advance. Untitled.png

Attached, thanks!

Perfect thank you so much!