Effective June 4, 2024, foreign workers working and residing in Denmark on a Short-Term Fast Track permit who extend their stay can continue working during the entire extended period without obtaining a provisional work permit, providing new biometric data or conducting a new identification check with Danish authorities (as was previously required) as long as their total stay does not exceed 90 days.
Short-Term Fast Track permits allow a maximum stay of 90 days within a 12-month period.
If one uses all of the 90 days within the 12-month period, affected individuals would need to apply for a new work and residence permit.
These reforms seek to give employers greater flexibility with respect to their short-stay workforce.
Source: https://www.fragomen.com/insights/denmark-work-rights-automatically-extended-for-short-term-workers-who-extend-their-stay.html