Solution found — see update to the original post above
Thank you for replying, the information you shared is helpful.
The reason I want to use several separate template documents is because each separate document needs its own separate page numbers. As described below, I believe there is no way to use a single template Rmd file to produce a Word document with several separate page numberings (each starting over from page 1).
In Word, I created a large, single template document that contains section breaks. Section breaks in Word allow a user to apply different page numbers within a single document. So, whenever I added a new document to the large template, I added a section break in front of it, and restarted the page numbering. The finished product is several separate documents, each with its own page numbers, from the single file.
While I hoped to be able to do the same in RStudio, it turns out this is not possible. According to officedown author David Gohel, Word section breaks are not recognized in Markdown. Officer and officedown are capable of allowing a user to apply complex style and formatting options to a docx template, but section breaks are not available.
I also looked at bookdown, but I was unable to find any tool that meets my need. As for latex, the best I could find was the possibility of up to three separate page numberings (TOC, main document, index?), but my templates contain 5 to 8 separate documents within a single file.
So, if there is no way for me to restart document page numbers within the same master template file, then my only other choice is to split up the template into its component document templates, pass the parameter value data to fill the placeholders within each template, and then render each template separately.
I'll look into whisker to see if I can get the same results with a single data set, but apply that same data to my several template files.