@maestrope My initial though is you may pinched them with the shims, especially since you stated that they operated easier prior tot he shims.

Thanks, @millworkman. I also thought the shims were the issue. However, I only used shims for two reasons: 1) to ensure the windows were plumb, level and square, and 2) to ensure there was no daylight at the side of the sashes when looking at them from the inside. My understanding is that we have to ensure both #1 and #2 -- it would be unacceptable to not have the window plumb/level/square, or leave the sashes so "loose" that one could see daylight. We used black plastic stackable 1/16" shims around the per pre-drilled screw holes, and it was mostly only 1 to 2 shims per hole -- in rare occasions, three shims, and some of the holes needed zero shims. The reason we actually used fewer shims than expected is that the windows were measured very precisely. Marvin Elevate frames are 3/8 shorter than the opening width, or 3/16 in each side, less than the usual 1/4 per side. But I did follow the instructions, and measured precisely -- perhaps too precisely -- and let Marvin deduct what needed to be deducted.

1) I will use the dry lubricant. It can only help. Any views on that?

2) We have not installed the trim yet. Should we remove some of the shims, risking that some windows would no longer be plumb/level, or risking some daylight from the inside? Also, we put some minimally expanding foam for windows and backer rod, so removing shims might mess up the foam at this point...

3) Instead of removing some shims, should we slightly loosen some of the screws?

3) I was actually at a Home Depot earlier today and tried some of the windows they have on display. There were clearly easier to operate. Should I assume that any window that is a floor sample, and not installed/shimmed in an actual construction site, would always be easier to operate? I'm just trying to get some perspective...

Experiment a bit before using the lubricant. Back the screws out a hair, you can actually tighten them again if needed. Although loosening the shims may not have the effect you are looking for, maybe pop a shim out of each side.

Take a look at the weatherstripping gaps.

These Marvin threads tend to get a bunch of posts...hmm

Thanks, @Windows on Washington Ltd. The weatherstripping looks fine, and we closed gaps (with shims) such that there is no visible daylight from the inside, as I understand should be the case.

The windows we have begun to re-check today are indeed plumb, level, and square, without excessive shimming, and with no daylight visible. Lubricant seems to help, and I will put some in all windows. I will also assume that time and use will "break in" the windows.

To be fair, opening them is an easy two-hand operation, but not an easy one-hand operation, and certainly not a one-finger operation. Perhaps I have been conditioned by some commercials vouching windows (usually vinyl) to be a one-finger operation, or by big box floor samples (uninstalled units) that are very easy to open. Is it fair to assume that a tight but perfectly operable (with two hands and reasonable effort) window is much better than a loose (and less energy efficient) window? Do new windows "break in" with time and use? And, are Marvin Elevate known to be tight to open?

Thanks, @millworkman. My apologies: I am not using my adjectives very well today. I should have said: they are a "not-too-easy but not-too-hard" two-hand operation. They are a rather hard one-hand operation, and an extremely hard (if not impossible) one-finger operation. Since they are plumb, level, and square, and do not appear to be over-shimmed, I will need to conclude that they will break in with time and with some dry lubricant especially made for windows. I guess "tight and not extremely easy to open" is better than "very easy to open and thus potentially too loose" in terms of energy efficiency. Thanks again.

Well...they will never be as "tight" as when they are new. The pile or compression of the weatherstripping is under the most tension when they are new.