As a long time user of the (Windows) "ASG (now Rocket) Remote Desktop" (ASG) tool, I would like to have the same convenience of separated account and host data in KRDC. ASG stores the data in a (shared) SQL database, so that users can share host definitions. These host definitions contain references to (eventually private) credential records, which allows for combining host and credentials as needed. Both host and credential records are presented to the user in a tree-like structure in the left window pane or in the menu. This also makes it possible to change a credential that is used by many hosts in one place only.
A few more details: When used with a database, each entry (host or credentials) can have a private or public scope. To connect to a host, the user needs to right-click it to get a context menu which has (amongst others) a "Connect as..." sub menu to select the credentials used for this connection. Both hosts and credentials can be organized in (nested) folders, where individual entries can inherit options from the upper level(s).