Im staying on resort, so I can start my planning at 7am. If I plan on going to the park late Afternoon evening, can I start building my day at 7am, and every 2 hours add another selection to it. So by the time I get to the park, I have like 4-5 things lined up.
I heard of the modify button, so would it just be modifying the times throughout the day to align with our park arrival.
Yes. (though again with 2nd pas booked 2 hours after the park opens). This is called stacking passes.
If you have to modify though it can get a little complicated keeping track of all the passes and time windows.
Another caveat is that in summer months, afternoon storms are pretty common. During storms, many attractions suspend operations. This happened to me last summer in MK. Storms arrived around 6:30pm, through roughly 10pm in MK. It has also happened to me in AK.
If this happens, the passes get converted to wild card passes. (any time that day, and can be used on most attractions).
BUT, you can only use them on attractions that are running. We wound up with quite a few any time passes, but few attractions were running.
Off the top of my head (I might be missing some):
MK closures: Barnstormer, Jungle Cruise, Aladdin, BTMRR, (Splash), Dumbo, 7DMT, and Astro.
AK closures: All animal attractions, Kali, Triceratops Spin, and EE.
Epcot Closures: I think just Test Track
HS closures: I think just Slinky.
While it is possible to stack for just the PM, that significantly limits how many passes you can book (because you wait 2 hours between each one). In HS, by mid-day, all the good passes are gone.
Also, come night time, we have often found standby lines to be fairly short for many attractions after 7:30-8pm. Last month, HM was walk-on at 10pm. It was POSTED as having a 45minute wait, but it was walk-on. Most of MK was walk-on, or near walk-on at 9:30pm and later. 7DMT and Space still had waits, but just about everything else was minimal.
Stacking can be useful, but it is a bit more of a gamble than booking/using morning and mid-day return times.