You can’t remove them but you could specify to open to another tab but then if the ClientUI opens for its normal purpose it will do the same thing for the end user as well.
_BESClient_ActionManager_InitialUITab
Type: String
Version: 8.0
Platform: All
Default:
Requires Client Restart: YES
Description: "Default: empty, decision left to UI default. If set to the non-localized name of a ClientUI Tab, causes the UI to open with that tab selected. Setting is case-sensitive. If no tab matches the provided name, UI uses its own default (currently the Offers tab)"