I would recommend you consider some other options besides building blocks if you have such an enormous number of sections. I don't think putting 2000 building blocks into a list is going to be a sensible workflow. The heading hierarchy is a key consideration if you are assembling docs from many parts.

Either of these two options might be a better match for your workflow and maintenance requirements.

1. Keep the content in a single template and create new docs by making a duplicate and going to outline view and selecting chunks for REMOVAL. This appears to me to be a more logical workflow if you start at outline level 1, then expand to level 2, 3 etc.
2. You could also create a macro to display the template headings in a Tree View where you can select elements for inclusion (which automatically selects all child elements) and unselect unwanted parts.

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Andrew Lockton
Chrysalis Design, Melbourne Australia