Review the prepared library before changing storage
An Android phone with expandable storage may offer internal storage and an SD card as download locations. Moving the preference should not be treated as a harmless label change while relying on already prepared travel viewing. Open the current Downloads list first and identify which items are still needed.
Read the documented storage consequence
Plex’s Android mobile settings say downloads can exist in only one location and changing that setting deletes existing downloads in the previously configured location. The control therefore is not documented as automatically migrating every prepared item to the new destination. Storage Limit is another setting, so increasing a limit and changing the physical location are different decisions.
Prepare a deliberate replacement plan
For example, someone adding an SD card before a journey should allow time and suitable connectivity to prepare the required items again if they choose the new location. Confirm the selected destination and verify the resulting local library on that device. Do not remove the only usable copies minutes before disconnected viewing. Keep this app-managed change separate from manually moving files in a file manager, which is not established by the storage preference as a supported migration method. If an item remains absent afterwards, report the changed location and download status rather than claiming a subscription or media-server library was deleted. After replacement downloads finish, open one of them from that device’s Downloads area.
Questions, answered
Does the documented location change promise to migrate existing downloads?
No. Plex warns that existing downloads in the old location are deleted.