Adobe Audition loses "clip gain" aftering Merge Clips

I have many small audio pieces for ONE track (please check my image). And I use "clip gain" to control the volumn/gain for each specific segment (please check my image - the yellow line). After completing the mixing process. I neeed to "Merge Clips" for ALL pieces on the SAME track. It will be easier to manage the project later.

BUT, aftering "Merge Clips", clip-gain-line is a straight line. All my volume/gain tweaks are gone. So please help me, how can I use "Merge Clips" and still keeping the "clip gain"?

Thank you.