Are there specific populations where GLP-1 medications haven't been well studied yet?

Yes. Pregnant and breastfeeding people, and pediatric populations below certain ages, generally have more limited data compared to the general adult population these medications were primarily studied in. Very long-term use (well beyond the multi-year trial periods) and certain specific medical histories are also areas where data is still accumulating rather than being fully mature. References: https://obesitycanada.ca/healthcare-professionals/adult-clinical-practice-guideline/