Give each grouping a clear purpose
An invented collection might contain a space-adventure trilogy, a standalone space documentary and a comedy set aboard a spacecraft. A franchise set keeps the trilogy together; a Space evening tag can gather selected films across those relationships. Kodi’s set documentation limits a movie to one set, so repeatedly moving it between two sets is the wrong way to maintain both views.
Create the list in the library
The official tag workflow begins from the relevant Movies, TV Shows or Music Videos library category, then Tags and New tag. Choose the items before confirming: the manual requires at least one title to create the tag. File view is not the same surface. Kodi also says movies and television shows cannot be combined into one tag, so a mixed evening plan may need separate lists rather than one assumed universal category.
Check the resulting organisation without moving the files
A movie set has its own editor under the library item’s management options. Tags can also become criteria in a smart playlist. These are ways to organise the catalogue, not instructions to move the underlying video into several folders. Open the franchise set and the themed tag separately and verify membership. If a skin exposes lists on its home menu, check that capability on the installed skin rather than assuming every theme provides identical shortcuts.
Questions, answered
Can one Kodi movie be placed in two movie sets at once?
The set documentation says one set at a time; use overlapping tags or another appropriate list for additional groupings.