Im burning all my old DVDs again with new software at a higher resolution than my existing copies I have in my Plex server but I dont want Plex to place these new versions at the top of the Recently Added list.
Disable Settings > [Server Name] > Library > Empty trash automatically after every scan (for being safe)
Run Refresh Metadata for the applicable items or Refresh Library Metadata for the entire library to ensure all items are matched using the selected library agent This should not be necessary but helps avoid accidents if you changed the library agent since you last refreshed metadata… in that case Plex could otherwise miss that any new files are duplicates / replacements of your existing ones.
Replace the files in question
Scan Library Files for the library
IF Plex shows that some of your items are “unavailable” after the switch, no harm should be done due to #1. IF Plex is considering the new file a different version of the same movie and expects 2 files to be linked to the items, you might need to manually trigger Empty trash on the library.
Alternatively you could try using a shortcut. If you replace the files using the exact same names, don’t scan the library for updates but Analyze the respective items. That should update the item with the new media characteristics while leaving it otherwise as-is (e.g. with regards to its “date added”).