@fatfatcoyote you can “save” here the container and the preservation procedure/protocol to be used for every single sample partition when the “preserve” transition is triggered, but the “Save” button does not fire this transition.
To do so, you need first to be sure you have the “preservation workflow” configuration option activated in Setup (Setup > Sample and COC > Enable Sample Preservation). A “Preserve” action should be available then in listings or in Sample/Analysis Request details view for “sample due” and “to_be_preserved” items. I suggest to create new ARs and test the preservation functionality with these new ones after enabling the “Preservation workflow” in Setup.
If after these changes, the problem still persists, please open an issue here: https://github.com/senaite/senaite.core/issues