Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Dear Tidi_559,
Good day. After thorough research, testing from my end and consulting, it’s been concluded that it is not currently feasible to add in bulk the members to the distribution list using Admin center.
You can add in bulk the contacts in admin center but not feasible to add them in bulk in DL via Admin. However, if you want to manage to add the contact in bulk in your distribution list you need to use PowerShell command.
We apologize if we are not able to meet your requirements; however, thank you for bringing this to our attention, we will surely raise you concerns to our Product Team and hopefully this can be included in the future updates. In the meantime, please feel free to post this in our Feedback community by visiting Exchange Online · Community (microsoft.com) as it is a community monitored by our Product team to help improve user experience with Exchange Online, via feedback given by our valuable customers. For other concerns, please do not hesitate to add you post in the Microsoft Community Team. Thank you for choosing Microsoft as your partner in business.
Sincerely,
Eben | Microsoft Community Moderator