Peanuts are definitely a good treat option if roasted and unsalted as mentioned.
Scrambled eggs aren't bad if there is no seasoning added however freeze dried chicken breast for example or other freeze dried hamster safe meats would be just fine without having to cook something(the cooking process does destroy some nutritional value,although in some cases like potato it is necessary but that is not the case with chicken for example in which freeze drying does not cook the meat but merely removes the moisture and keeps all the nutrients).
If you want to offer more than one type of nut over time you can certainly use walnuts in place of peanuts however it is not necessary.
Sunflower seeds are already in good quality mixes(Harry Hamster in the UK,or in the US a combination of Higgins Sunburst and either Mazuri rat and mouse lab blocks or Carefresh hamster/gerbil with the Carefresh version needing animal protein added with every feeding)so adding more of them is not necessary and could become unhealthy.Too much of a good thing can end up being very bad!
You could use different seeds than chia and feed those more frequently,for example flax seed.Just make sure the seeds are a safe type and not found in your daily diet already.
Yogurt drops,as with most other storebought treats,are loaded with sugar and other unhealthy things.Dairy in general isn't good for hamsters either(some will disagree,but it certainly isn't a necessary food and there are many things that would be more natural and suitable than diary products).I've noticed the baby versions can sometimes be slightly better but they still aren't something you want to feed often(once or twice a month at most,if your hamster even likes them)as they often contain gelatin(boiled bones,very difficult for any animal to digest).
I've never seen a hamster food without corn in it,so popcorn and corn are both unnecessary and would be a bit pointless to feed(they'd add no diversity to the diet,therefore being pointless extras).Celery is fine though in moderation as with any extra food in the diet.
Bread is very difficult.Most would have added processed or artificial sugar along with other unhealthy ingredients,so I would avoid them in general.You can do more good with straight grains rather than heavily processed bread!
Cooked potato or sweet potato can be good in moderation.With any foods,aim for non-GMO and pesticide free things(not necessarily organic as this is not a guarantee of safety,since some organic produce still contains harmful pesticides that are merely natural versions of chemical ones).
Pasta wasn't liked much in my experience,but it is worth trying out if you find good quality pasta(simple ingredients,nothing artificial,etc).
Baby carrots,apple,and banana are all fine as long as there are no additives as with any fruit or vegetable.I would avoid grapes though,as there are plenty of less risky fresh foods to offer
The other fruits mentioned should be fine though.
As for corn flakes,you face the same issue as with other corn products.It wouldn't really offer variety with hamster foods containing corn anyways,so once again it would be a bit pointless.Lots have added sugar and unnecessary additives(often loaded with artificial ingredients too),so that is another issue.
Make sure any food or treat you offer does not use vague terminology for ingredients,unspecified or unhealthy biproducts,artificial ingredients,etc.For example with unspecified biproducts you'll see things like derivatives,digest,meat and bone meal(or similar using specified meat,regardless it is equally unsafe no matter which is stated),animal liver(can come from just about any source including unsafe ones like roadkill as with any unspecified biproduct or meat ingredient),or just "liver" on its own with no true identification of the source.You may also see E&C approved antioxidants or something similar,which is not something you want as it is a loophole term which allows manufacturers to hide what preservatives they really use(including BHA/BHT/ethoxyquin which are known to cause cancer especially when used over time although it is never a good idea to use products with these things in them)or E&C approved dyes etc(artificial dyes).It can be very confusing to filter through things,but with a bit of open minded learning it can all become very simple