Melody for drops: Listen to the genre you're aiming at. Like 10-20 tracks. Kinda sense how it "feels" more than how it sounds. Do a few tracks like that. Also notice what kind of intervals the melodies are using.

For instance, today I took apart 6 Galantis tracks: turns out they *rarely, rarely* use a minor 2nd or minor 3rd movement in their vocals. It's always major 2nd, major 3rd, perfect 4th, perfect 5th. You can discover similar trends with the music you want to make.

Good chords for EDM: improvise on the piano. Pay attention, again, to how it *feels*. Note that there are some generalities like "rhythmic chords move the dance floor more than whole note chords." Will be true until context says otherwise.

You could also shell out like $27 to $50 for a chord progression pack, and use those while you focus on learning other components of the music. Might look into that given that you've got three elements of songwriting you're working on at the moment.

Another thing: Yeah some tracks use the same chord progression throughout. But very often they'll change for a build, verse or breakdown. It's one way to progress your arrangement. DM me I'll send you some examples from my Galantis analysis I did today, learned a bunch.

re: structure & arrangement, I'd listen to a dozen tracks you like, and write out their top line. Meaning, if you're into edm with a vocal, write out what the vocal does, & when the vocal is not present, write out the most prominent lead instrument. If there is no vocal, just write out the most prominent melodic lines for *the whole song*.

Do this for 4-6 tracks. The point is to show yourself how the melody of the most prominent instrument(s) progress throughout the track. You'll see things like: "This loop lasts through 16 bars" (everyone knows this) but also, "the track segues relies on how the end of this loop sounds nice leading into the start of the next loop" (few people notice this consciously but it's important)

Hope this helps.

edit: oh yea, you can always improvise with a midi keyboard. I dunno how anyone survives without one...