Hi @Pto,
Welcome to the community 
For bulk import/update there’s a method that @Victor introduced and explained here! : Bulk operations and Timer Tricks, part 3: mass update for the records , Countdown Timer tricks: how to clone list item with all sub items using countdown timer
But I guess this would get slower when the records grow! ( Maybe Victor can explain this well? ) I think you could use MAKE here too but not sure the performance.
You can add this feature request here : https://adalo.canny.io/
Thank you