boolean setRecentlyUsed(DataType dt) {
		if (dt != recentlyUsedDataType && !dt.isDeleted()) {
			recentlyUsedDataType = dt;
			if (programDataTypesManager != null &&
				dt.getDataTypeManager() == programDataTypesManager) {
				recentlyUsedDtId = programDataTypesManager.getID(dt);
			}
			return true;
		}
		return false;
	}
Sets the given data type to be the recently used data type.  
@return true if the data type was added; false if the data type
is already in the recently used list
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/DataTypePropertyManager.java