If I understand your question correctly, you are asking how to represent blanks within tables when those blanks are meant to be filled in.
According to Braille Formats, Partially Filled-In Tables (section 11.9) should be transcribed with a dash for each blank cell that is meant to be filled-in. If your table with a blank that is meant to be filled-in is transcribed in UEB, use the UEB dash (6, 36); if your table with a blank that is meant to be filled-in is transcribed in Nemeth, use the dash appropriate to the Nemeth Code (36, 36).
If your table is transcribed in a listed format, follow #11 under Formatting in the Guidance for Transcription Using the Nemeth Code within UEB Contexts. That is, use the double dash (36, 36, 36, 36) for blank entries that are to be filled in.
Braille Formats (section 11.6.5) says that a series of dot 5s should be used "when the column entries are empty and are not meant to be filled in by the reader."