One Microsoft account = 15 root domains, so Pass splits it into 15 "sites." For example, a login saved on live.com isn't offered on microsoftonline.com, azure.com or office.com.

Microsoft's list: microsoft.com, live.com, microsoftonline.com, office.com, office365.com, cloud.microsoft, azure.com, windowsazure.com, xbox.com, bing.com, msn.com, hotmail.com, windows.com, microsoftstore.com, passport.net

Bitwarden ships this exact group built in. Apple's password-manager-resources repo groups them too.

Ask: built-in equivalent-domain groups, user-defined groups, and a "merge duplicates" button.