Yes, it is possible.
In the Annotated Model Grant Agreement, p. 509 (Budget flexibility box) it is written that:
“Research, training and networking unit costs should be used for the research, training and networking activities foreseen in Annex 1, but unused amounts may be used for other action-related purposes (e.g. to cover travel and subsistence costs of a staff member, to organise additional training activities or horizontal networking events).
Unit
costs for management and indirect costs should be used for the management of
the action, but unused amounts may also be used for other action-related
purposes (e.g. to cover travel and subsistence costs a staff member, to
organise additional training activities or horizontal networking events).”