It’s so awkward getting the correct syntax with so many changes happening over the last few years.
You are not specifying SelLength so its anyone’s guess as to what text is being selected.
This is untested forum code, try:
TA.SelStart = Len(TA.Text) 'Put the selection start just before the text we add below/at the end of current text
TA.AddText SQLite_RS.Field("tbl_Name").StringValue + ":" + EndOfLine
TA.SelLen = Len(TA.Text) - TA.SelStart 'Select the text just added above
TA.SelBold = True 'bold the selection
TA.AddText SQLite_RS.Field("sql").StringValue + EndOfLine + EndOfLine