Multi-Tasking is one of the many new features introduced with The Sims 4, and the always awesome SimGuruGraham has clarified a few things over at Mod The Sims.
Inge Jones asks: Graham, will a sim who you have told to paint a picture be able to take a quick bathroom break and go back to painting without the player have to tell them to paint again?
Graham replies: Nope, that would be a sequence of tasks and not a form of multitasking. As in previous games, you could direct a Sim to paint, then use the bathroom, then resume painting, and the extra interactions would wait in the queue until they could execute.
Alternatively you could ask me, “Graham, will Sims be able to multitask by painting a picture while using the bathroom?” to which I would also, sadly, have to answer “no”.