I will stay at home tomorrow in the evening.
Toată lumea trebuie să rămână acasă în timpul Covid 19... Everybody has to stay at home during Covid 19...
They never explained before that "o să" means anything special, nor did the mark it in yellow to indicate this is a new term.
Can this not mean "I will sit at home tomorrow evening"?
A sta is a general word indicating that someone is stationary. To mean to sit it needs some additional specification. I think o să stau jos could do.
Why not 'eu voi sta acasă mâine seară?'
This is a good example too☺