This request is one possible solution of more general Related feature request:
Details about opening the focused file in active pane are also mentioned in subsequent comments there.
Do you want to keep this as separate request? I would probably prefer to merge it into that one with support of over 58 votes/likes and discuss specific implementation details there.
I think that list of files (or search results) would benefit from having some “focus pointer/cursor” like the “caret” in text editor.
As mentioned deep in the other thread:
Similar would be useful for keyboard navigation in Search results requested e.g. in:
https://forum.obsidian.md/t/from-search-bar-arrow-down-through-results/5917