We can define a maximum quantity of generations for each member in a PDSE version 2 data set.
In more than one place in the ISPF Edit and Edit Macros manual (SC19-3621-01) there are implicit indications that we can edit a member generation different from the "generation zero" (the most recent one), but there is no explicit information on HOW to do such an editing.
After some search, I found this info in the ISPF User's Guide Vol.1 (SC19-3627-01):
Consider the following items when using line commands with members in a PDSE version 2 data set that is configured for member generations:
v When you use the B, E, or V line command to browse, edit, or view a member, you can use the Prompt field to access previous generations of the member. In addition to entering the line command, enter a slash (/) in the Prompt field to display a panel on which you can enter the generation that you want to access.
v When you use the D line command to delete a member, the current generation and all previous generations of the member are deleted.
v When you use the C line command to copy a member, only the current
generation of the member is copied.
v When you use the M or R line command to move or rename a member, the
current generation of the member is moved or renamed and all previous
generations of the member are deleted.
Hope this be of some help to the people that is beginning to use such a facility.