Mettā and Prajñāpāramitā
One of the descriptions of bodhisattva activity throughout the Perfection of Wisdom literature is that they radiate the brahmavihāras—lovingkindness, compassion, appreciative joy, and equanimity. These classical states of unboundaried positive emotion are both specific feelings and specific nondual meditative states.
As meditative practices, the brahmavihāras begin as methods to confront the unconscious identity-defining boundaries of friendship, relatedness, and tribalism that cause so much suffering in the world. As they grow, they are meant to more fully uproot the suffering based in vedanā: liking some beings and disliking others. At their fullness as meditative states, they overcome our inherited view of the distinctions between beings as being indicative of any worthiness of love.
This sequence is true for all the nondual meditations. In the beginning, they help us tolerate unpleasant experience by practicing accepting that things are as they are. This grows a basic emotional intelligence. As the practice deepens, they ask us to heal those places where we cling to bias, preference, and identity as sources of security. Until we find significant resolution of old emotional patterns, we will not be able to stabilize the heart in concentrated rest (samādhi).
Nondual teachings in the absence of samādhi are likely to be spiritual bypass, but if there is stable samādhi, there's no bypass. You can't talk your mind into deep embodied presence.
All of this cultivation is still "dual," in that it is a training of the attention and purification of the heart. The truly "nondual" aspect of nondual meditation only blossoms when the primary quality of the state—love, compassion, joy, equanimity, emptiness, spaciousness—becomes unbounded and limitless.
Bodhisattvas "save all beings" because they rest in samādhi that is stable and limitless. They stabilize on any quality that can become boundless, mainly the brahmavihāras and emptiness. If we feel the heart intention to practice bodhisattva activity, training in samādhi may be more important than we commonly assume. Bodhisattvas without samādhi are not bodhisattvas.