How to create index in PowerDesigner

In general, when I design data model in PowerDesigner, my process is:
1. Create CDM
2. Generate PDM from CDM.
3. Generate script.
If I modify data model, I modify CDM then generate to PDM, the process like above.
But, how to create an index of one table?
CDM can’t create an index, only PDM can do it.
In my process, I create an index in PDM, next time I generate from CDM, the index disappeared.

my solution

1. When generating PDM,  select "Preserve modifications" in the “PDM Generation Option” dialog

2.  Comparison Option set not include Table > Indexes
Click [Set As Default], next time won’t need to set again.

3. Generate PDM always accept all actions without remove table index.

display index on PDM

1. Open PDM, Select Menu > Tools > Display Preferences
Click Table
Select Index and Indicator of Index check box.

Apply to All symbols / Selected symbols.
Then it will display like below: