How bad did I screw up?

I added my malt extract to my wort added my bittering hop boiled for 40 minutes aded my flvoring hops boiled for 20 minutes and realized that I forgot my maltodextrin. So I added it and boiled for an additional 20 minutes. How bad is this?

The flavoring hops won't give the most flavor or aroma at 20 minutes. It should be 15 or less. I don't know anything about malto dextrin but it doesn't seem like you really screwed anything up.

your bittering addition turned into an 80 min addition and your flavoring addition is now essentially another bittering addtion because it boiled for 40 min total. The beer may be more bitter than anticipated and will lack some hop flavor, but it should still be OK.

What style of beer was it, what hops did you use, and what were the alpha acids?

well, you probably won't get much flavor from the flavor hops as they were boiled for 40 minutes (even 20 minutes is a really long time to impart flavor). Consequently, you probably derived more bittering from those flavor hops than anything. Likewise, you may have extracted more bittering from the bittering hops in the longer boil.

As far as the actual "oops"...you could have added that right at flamout without any problems. No need to boil that additional 20 minutes. As long as it is dissolved it would have been fine.

In fact, the conventional wisdom these days is to NOT boil your malt extract for the full time, just add a bit at the beginning, boil for the indicated time to extract bittering and then majority right at flamout. Again, if its dissolve then its good. Boiling malt extract increases carmelization and darkens the wort.

All in all, it will be fine..

Are you supposed to add it at the beginning of the boil? IMO, your brew will be fine and the only thing you may notice is that your beer doesn't have as hoppy and aroma as your finishing hops were boiled longer than usual. I bet you will be happy with it.

Same as above. You might notice less hops, but that's really it. Not a big deal.

Actually, you will have more bittering as all the hops were boiled longer. The longer you boil the hops the more bittering they make. It also drives off the hop aroma and flavors. So more bittering and less hop flavor and no aroma. But really it's not a big deal. RHAHB

FYI: I don't think you really needed to boil the malto dextrine for so long. A minute or two would have been sufficient to sterilize it. OR you could have added it to the fermenter later during fermentation. Just boil it in s small amount of water and add that in during fermentation.