No one has answered my question I did a bit of research and figured out how to create my own template. For the sake of those who come along later, I am describing what I did so that others will have a head start.
First of all, I have no idea if anyone on the development team for Libre Office is generating templates for new labels as they are released to the market. There are a lot of templates for commercially-available labels already in the program so someone must have done the work to create them but I don’t know if new labels are systematically added to Libre Office. Perhaps the labels I have are so new that they simply haven’t had a template developed yet and the developers will add them to the product soon. Or maybe they only get created if there is a significant demand for a given label. I leave that for others to determine.
Also, I should mention that the label companies - or at least Avery, which is the only one I checked - do have templates on their website but they are for Word, not Libre Office. I have no idea if a Word template will work in Libre Office and didn’t try the Word template for my new labels.
Since I had no template and wanted one, I thought about creating my own, although I had no real idea how to proceed. I looked at the Writer Guide to get the basic concept that I needed. Although the Writer Guide is a bit dated now since it is targeted at Writer 4.2 and I am running 220.127.116.11, the Writer Guide still seems accurate on the subject of templates, at least to the limited extent I looked at that chapter. The Writer Guide made it clear that I could simply develop my own document and then save it as a template and put it in the “My Templates” area. That was the key concept I needed.
I created my document quite simply. I began by finding a ruler and removing one of the label sheets from the package. I measured the following things: the size of the label sheet, the margins (top, bottom, left and right), the height and width of the labels, and the width of the space between columns of labels (I think these are called gutters). I also counted the number of labels in a column and the number of columns on the sheet. Then I created a new document. I formatted the page first by clicking on Formats->Page… then chose the Page tab. I chose the proper page size and orientation (which is normally portrait for label sheets). I set the top, left, right and bottom margins, then closed the Page properties.
My labels, for the Avery 6468 labels, are in 2 columns of 5 rows each. I determined that there was no obvious way to leave space between the columns of a table so, rather than creating a table that was 2 columns by 5 rows, I created a column layout. I clicked on Format->Columns… and set the number of columns to 2. I clicked the option that said to make the columns equal in width. I unchecked the Autowidth checkbox and entered the actual width of both columns, which was 3.5 inches, and the width of the space between the two columns in the box labelled Spacing.
Then, I created a table that was 10 rows by a single column with the intention that the first five rows would go in the first column while the last five rows would flow to the second column. Initially, the table stayed entirely in the first column and the row height was far less than I wanted. The row height seems to default to a fairly small size. I fixed that by clicking on Table->Size->Row Height…, then unchecked Fit to Size and set the height of the rows to the actual measured height of the labels. After I clicked OK, the table flowed exactly as I wanted it so that the first five rows were in the first column and the second five rows were in the second column.
I haven’t actually tested the document yet but plan to in the next couple of days. I’ll simply put some text in each table cell, load a sheet of the labels in my printer, and print that page. If any of the text prints outside of its intended label, I’ll tweak my margins, row width, row height and space between columns until everything lines up perfectly. Then, I’ll follow the instructions in the Writer Guide to make it a template and put it in “My Templates”. I may even offer the template to the development team to incorporate in the next update of Libre Office.
Anyway, I hope this helps someone.