StartAt Time has been added and you can use a few different formats.
example url using the "t=" option: https://www.youtube.com/watch?v=Tw-WbgyfoYk&t=300
To start at 5min, you can use: t=300
or t=300s
or t=5m
To start at 4hours 19 mins, use: t=15540
or t=4h19m
or t=259m
so on..
Oh, good. I have my browser so locked down that sometimes I end up wondering if the problem is on my end or not.
So if I understand you, this should expando: https://www.youtube.com/watch?v=Tw-WbgyfoYk&t=300
And this should not: https://www.youtube.com/watch?v=Tw-WbgyfoYk&t=300
And this should expando but not https://c8.alamy.com/comp/B52A7K/bad-habit-domestic-cat-eating-spaghetti-B52A7K.jpg
Edit: videos do not expando.
Edit edit: Images always expando.