Battled NPC's and collected overworld item flags

[Macromind101]

Mainly asking for the switch games but can be extended to all games as well. Are there any methods or tools that can be used to edit (or just check) whether an NPC has been battled, or if a non-respawning overworld item has been collected? Also could be a way to quickly check and see what NPC's and items have been skipped without having to manually backtrack.