Batch Conditional Action Save (overwrite not Save As)

The action panel menu offers an insert menu item so that certain commands can be inserted , which is not a magic bullet but still useful.

Which script you are using for Batch processing? File > Automate > Batch, I guess. That script offers to overwrite Save As command. If you want to use Save command then @c.pfaffenbichler gave you good explanation.

All action steps are independent, can be played on its own but... each and every step has dependency like previously explained: particular command which should be executed must be available in menu like some layer or particular layer must be selected or pixel based layer must be selected to apply filter, or some changes must be made to activate Save command like in your case and so on... Confusing part is that you can record step which may not be available for execution when playing action.

»the option to just Save is not available«

Save is in pronciple possible in Actions if it is possible in the current situation – so for example if you added Layers to a jpg you need to make the image conform to jpg’s possibilities again before being able to save it »plainly«.