Can actions be copied or moved from one macro to another?
Yes, but it was not obvious to be either at first.
Put the source Macro in EDIT mode.
The select the Action(s) you want to copy/move, by click, SHFT-click, and CMD-click.
Press the normal keys to copy (CMD-C) or cut (CMD-X).
Switch to the destination Macro, and put it in EDIT mode.
Select (click on) the Action where you want to insert the source Actions AFTER.
That’s it!
As @JMichaelTX says, you can simply copy & paste the actions from one macro to another.
Note that there is really no need to ever turn Edit mode off - you can simply leave it on, and for the most part that is how I would recommend using Keyboard Maestro.
If you’re concerned about when a macro is saved - macros are saved more or less instantly after any change (there is a small delay to allow multiple related changes (like typing) to be made at once). There is no need to turn off edit mode or otherwise do anything to save the macro.