This is more complex than you'd initially think. Not because importing from Excel is hard, but because of all the edge cases and possible inconsistencies in the data. In Pigeon Planner, the bandnumber consists of 4 parts, so the Excel sheet needs to have 4 columns as well that match those. Same when parents are provided. Also some data like sex is stored as a number (eg. cock=0, hen=1, young=2), which means there needs to be some mapping between the user's data and expected values. Other data that's just stored as a string (colour, loft, ...) is not a problem.
What about handling existing pigeons? In which columns is which data? It's more involved than just reading the file and adding it to the database. I mean, it's not impossible, but probably too much work for how much it'll be used.
There is however a very basic tool to add many pigeons at once, see File=>Add range. It still uses the old 2-field bandformat and is limited to just numbers, but it's a start. Maybe it's just best to extend this a bit more to handle a few different things.