https://www.palantir.com/docs/foundry/platform-security-concepts/projects-and-roles/#create-new-role-sets describes how to create custom role sets, and includes an example of a role set containing "Editor without ability to sync."
In general, it seems that "X without Y" is a useful concept ("Viewer without ability to export" is another example); however, it doesn't seem that there is a first-class way of defining a custom role in those "subtractive" terms, so in order to create such a role, it is necessary to manually copy all of the operations except for a small subset from the original role (which also means that any new additions to the original role will need to manually be added in the future, if we want to keep them in-sync).
Is my understanding correct that there is no convenient shortcut for this use-case?