Bifold windows?

[WindowsQuestion]

We really like this look for a new kitchen extension.
Does anyone have bifolding windows? Are they any good?

I don't have these windows but they're very 'fashionable' at the moment as I see them on TV reno shows all the time. I always wonder though:

1. what if you just want to open the window a crack?
2. how many opportunities are there to open them fully in a British summer?
3. do they make the house easier to break into?

Sorry to put a dampener on the idea...

Yeah that’s all concerns I have too.
Plus expense…
We’re having big sliding doors on another aspect of the kitchen instead of bifold doors.
Might go for more conventional windows, or one long one

We have them in the bedroom and lounge ( full length ) they are great ! We have the bedroom open all summer. You can put them on the jar , but ours can’t be locked like that , maybe others can ?