Saving private tabs in sessions (question)

[Tallefer]

Could you tell please, if possible, what are the last versions of Private Tab, Firefox and Session Saver, that are able to save private tabs in sessions? Unfortunately, I've lost track of it at some point and now there are too many combinations to try manually.

[Infocatcher]

Things about removing private tabs from session data was moved into Firefox code: #82, bug 899276.
It's still possible (before Firefox 57+...) to alter some Firefox internals, but the way is very tricky (and buggy).

[Infocatcher]

And about Firefox 57+: #254
Saving may be possible, of may not: depends on API (still not implemented) from Firefox side.

[Tallefer]

Thanks, so the main line is drawn somewhere after Firefox 25, right? Is the version of Private Tab important? Also I don't care much for 57, staying on ESR 52 for now.
Earlier I was able to save private tabs, then I migrated all my sessions to 52 and...

• Got this: https://i.imgur.com/bhKQYDP.png
  Note the purple color, it means private mode, those cannot be selected, but you still can middle click on them to open.
• And this: https://i.imgur.com/bzAow7a.png
  All tabs were saved and treated just like normal tabs.

I want to find a combination to get the first result, at least.