How does one combine intentions in supererogatory prayers?

The two prayers that can be combined in intention are:

- Those where neither is intended for its own sake, but rather the intention is to occupy the time with prayer, such as تحية المسجد (greeting the mosque) and سنة الوضوء (Sunnah of ablution).

- Or, if one of them is not intended for its own sake and the other is intended for its own sake, it is permissible to combine them with the intention of the prayer that is intended for its own sake. This will earn the reward of both prayers, such as a راتبة (regular Sunnah prayer) and تحية المسجد (greeting the mosque).