Is it permissible to sit down to read the nawafil namaaz including namaaz e shab? Or do you have to read double the number if sitting?

All Nafilah prayers can be offered while sitting, but then, certain Fuqaha say that 2 Rak'ats prayed sitting should be counted as one Rak'at. For example, if a person wishes to offer Zuhr Nafilah which consists of 8 Rak'ats, in a sitting posture, he should offer 16 Rak'ats. And if he wishes to offer Witr prayers while sitting, he should offer two prayers of 1 Rak'at each. This later preference is not known from any sources; however, they may be followed with the hope of earning divine pleasure.