Is it possible to merge multiple rows into single value using report definition?

Index table may have more entries for single case but while displaying we need to merge couple of columns of index table into single value .

W1 Index1 Index2

W1 Index3 Index4

while displaying to end user : W1 Index1,Index2,Index3,Index4

I don't see any OOTB function alias to support this usecase . If anybody has achieved the same using report definition rule then please advice here .

we had performance issues with present approach .

1) Using data page ,Fetch results from index table each WO record

2) Have a section to display multiple results using data page .

3) Refer this section as column to the grid view which display case details .

we're looking at function alias code snippet/better approach that can be achieved with in report definitions.

Pega 7.3.1