There is a fair chance that these windows are common property and even if they aren’t, they probably shouldn’t have been altered without some sort of formal permission.
Judging by your other posts, two things occur to me:
1. Your strata scheme has been allowed to trundle along with few controls on what people do with their own and common property.
2. You are gearing up to bring everyone into line.
If this is true I would caution your that the reason the scheme is run like that may well be because that suits the majority of owners and tenants.
However, if you want to get everything sorted out, don’t try to do it all at once and don’t try to do it on your own. Have a chat with your neighbours and see what their priorities are before you set the ball rolling.