A couple of scripts that worked in earlier versions of ID
1. One is a script wrote by Manan Joshi that indeed inserts a row at the end of the table not in the character style indicated in the code but in the style of the row preceding it.
table.rows[-1].cells.everyItem().texts.everyItem().appliedCharacterStyle = “myriad regular”
**********
Manam wrote another version that gives this error.

app.documents[0].stories.everyItem().tables.everyItem().rows.add(LocationOptions.AT_END).cells.everyItem().appliedCellStyle = "StyleName"https://community.adobe.com/t5/indesign-discussions/it-is-possible-to-add-one-row-or-a-line-of-text-at-the-end-of-a-table-in-a-document-with-many-table/m-p/11727702
/////////////////////
2. The another one, by Jump_Over, gives an error 21: “undefined is not an object”.
app.documents[0].stories.everyItem().tables.everyItem().rows.add(LocationOptions.AT_END).cells.everyItem().appliedCellStyle = “EndRow”
