Your issues could be resolved easily enough by removing the entries that you never want to use.

It can be useful to remove all the existing entries from the Built-In Building Blocks.dotx template if you are actually putting in your own entries. For me, the huge number of entries there are good for sparking ideas but in a corporate environment they just get in the road of productivity.

Deleting all these entries is not irreversible because you can remove the template from %appdata%\Microsoft\Document Building Blocks\1033\16 (or whatever location relates to your language and version) and it will be recreated by opening Word.

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Andrew Lockton
Chrysalis Design, Melbourne Australia