When using the Directory Manager UI, Cache Indexed Attributes exists on the DSA Server tab. However, one may have difficulty to add additional attributes there using the usual space, comma, or tab key and was commonly suggested to use the "Raw Settings" tab to do the work instead.
Symantec Directory 14.1
This is because it is for fields like cache-index, the UI is not designed to show you a list of options to pick from as the number of the options for this type of fields could be too many or unreasonable to expect the UI to provide the list. As such, for those fields where UI provides the possible options, the UI behavior is actually different.
For this type of the fields, one will need to know the exact string to enter. Then instead of using the commonly used space, comma and/or tab key to insert the values, use the <Enter> key instead and see the UI actually takes the data in and also shows a cross sign to allow one to remove it.
Part of the reasons to not allow space or comma to mark the end of the desired string is that there are possibilities the string being entered may need to embed space or comma in it. As of the tab key, to move to the next field on the UI already.