I have a question about whether it is possible to place a variable in the offset number in the scheduled path? A Variable that can be modified outside the flow to avoid stopping the flow and modified it when is in production? I use this schedule path to send an email alert 31 days before the end working date. Can it be performed with apex? Or practically that requirement cannot be accomplished?
You're thinking about this from the wrong direction.
You can create a new Custom Field (Formula), and specify the metadata:
(Warning End Date): Returns Date
EndWorkingDate__c - $CustomMetadata.TimeDelay__mdt.DefaultValue.Offset__c
Then, in your Flow, specify (0 Days Before) (Warning_End_Date__c). A word of caution, though; records that are saved before the offset value are changed will not honor the new date unless they are edited before the scheduled path executes.