What is best way to reuse content amongst multiple documents?

Another option besides those suggested by Charles: Insert a bookmark around each table (and its caption, if any) in the source document. In the other documents, place an INCLUDETEXT field containing the filename of the source document (and its full path, if it isn't in the same folder as the document) in double quote marks, followed by the name of the bookmark on the desired table.

For example, if the file containing the tables is table_sources.docx, and a table containing information about colleges has the bookmark name Colleges, the field code would be

{ INCLUDETEXT "table_sources.docx" Colleges }

or perhaps

{ INCLUDETEXT "C:\Temp\table_sources.docx" Colleges }

Note that backslashes in a path must be doubled in the field code.

When the fields are updated, they'll show the tables. If the tables in the source document are edited, the fields in the other documents must be updated (Ctrl+A, F9).

1. Quick Tables which are Building Blocks and to make any changes you would need to (a) modify and save the Quick Table, and then refresh in recipient documents.
2. Mail Merge is my favorite, with data stored in Excel and reflected in other documents/templates.

Thank you. We may try this. In the interim, added the subdocuments and then unlinked them. They don't get changed often, so figured better to stay safe and not worry about linked files.

Do look at my page Master Documents "Feature" in Microsoft Word.

"It has serious bugs and will corrupt your entire document at the most inconvenient time possible. (This advice to not use Master Documents reported as correct through Word 2021.) John McGhie put it succinctly when he said that "there are two kinds of Master Documents: Those that are corrupt and those that will be corrupt soon." It was reported fixed in Word 2007, but "The jury is in: The Master Document feature in Word 2010 remains word processing's answer to Conan the Destroyer. Use it only if you enjoy pain and frustration." Microsoft Word 2010 Bible by Herb Tyson, MVP. "Since its inception, the Master Documents feature has been a bit quirky and buggy, and that fact hasn't changed with Word 2010, unfortunately."  by Faithe Wempen, p. 681 This comment has been updated without change (other than the year) in Microsoft Word 2013 In Depth and Microsoft Word 2016 In Depth."

If you are using this, make regular backups of your documents that are offline.

Thank you. We may try this. In the interim, added the subdocuments and then unlinked them. They don't get changed often, so figured better to stay safe and not worry about linked files.

Thank you.