several.
one is fighter_II A to fighter_II B as one of many plane samples
several old tank versions to a newer version ... both with the same and with new chassis
old infantry equip to newer one
old arty/anti tank/anti air to new one
nothing, literaly nothing is working. there is plane and simply no upgrade button.
and yes i decomissioned countless tank and plane designs..
OK, so in order to upgrade the equipment it has to be in your stockpile...NOT currently being used by your divisions...AND marked as Obsolete*.
So if all of those Fighter IIA are currently assigned to active air wings...you can't upgrade them. However, as you produce new Fighter IIB, the IIAs will move to your stockpile (assuming you aren't also trying to build them up to full ToE). Then once you have them in the stockpile you can check the upgrade box and start upgrading them.
Infantry equipment can't be upgraded (and has never been able to be), same for Art/AT/AA.
Tanks are mostly the same.
Equipment to be upgraded from has to be marked as Obsolete*, in the stockpile, and the same generation**.
It was planned to make the conversions much quicker, but they can't seem to get the code right*** so they removed it and the only savings is not having to re-supply the special resources except for *new* ones.
* Marking captured/Lend-Lease equipment Obsolete isn't possible, so you can only convert these if the original country marks them...which for countries that no longer exist (i.e., not a GiE) isn't possible.
** Prior to NSB, you could convert either the current or previous generation to SPAT(TD)/SPArt/SPAAG, but that changed with the new system and you can't change the chassis generation.
*** It was quickly pointed out that it would be quicker and cheaper to build AFVs using a two-step process. First build the Chassis with minimal equipment and then upgrade to the final design. So they changed it quickly to just be reduced resource cost (i.e., you don't have to pay the same resources twice), and factoring in any conversion speed boni.
