I gather this is from Bentley Structural?
You can turn off names for a member type or even a section name using macros, but I don't think you can for a single member. If this member isn't going to be used any way then deleting it would be a better idea.
You could try mapping the "dummy" member to a default steel shape, maybe a very large one or a rectangular shape, etc. (something not being in prevalent use in the rest of the model). There is an option to set the the Default Section name in the RAM import dialog box, this is used to create 'default' members when the member being imported does not exist in the steel table being used in Bentley Structural. So if you have the member in RAM that is not in the Bentley Structural table it will default to whatever you assign here.
You could then use Select By Attributes to select all the dummy members at once and then delete them.
Please let us know what version you are using.
There are probably some other ways to handle what you want to achieve, this is my initial thoughts...
Thanks for everyone's comments. I'll experiment and see which works best for me.
Jerry