Why you should not change slots, and how you can anyway

[el cid again]

There are two different reasons the Manual says "something in a slot can be changed, but it never should be moved."

Reason 1: In most cases (there are a few exceptions, thank goodness) the editor is very stupid. IF you move something - pointers referring to that something will NOT move. So now they point at something else - or nothing - that is they keep pointing at the old slot. Aircraft are an exception - partially. IF you move an aircraft, SOME pointers will move, while others will not! But ships? IF you move a class, ALL vessels will NOT point at the right class any more!

Reason 2: In a few cases, hard code assumes something is in a particular slot. For example, a support squad, a motorized support squad, an atom bomb, a malaria free hex in the malaria zone, Bataan, Singapore, Chitose, Chiyoda, Ise, Hyuga and other things are in dedicated slots which will continue to pretend those things are there even if you move them.

Now you can dishonor the directive and move things to a different slot.
But you need to do so in an informed way.

You can beat Reason 1 IF you find ALL pointers to that slot and MOVE them too.

You can beat Reason 2 IF you WANT the code to work with a different something - or if you no longer want it to do that at all. For example, if you don't want Ise and Hyuga to upgrade to semi-carriers, it is OK to move them to a different slot - and put NOTHING in their slot. [Or better still 9999 in the delay field]. Or if you want a hex to be Malaria Free (e.g. Baguio/Balinta Pass) - then you can - and MUST - put it in one of the few Malaria Free slots - and whatever used to be in that slot will now be "infected" - as it were.