Checkboxes are not supported in RTF, but for tables, you can add rows by pressing Tab while in the bottom right cell. To add columns, open externally (Ctrl+J) in Word or LibreOffice and add the column, then save and resume internal editing in UR (Ctrl+Shift+0).
https://kinook.com/UltraRecall/Manua...externally.htm
By headings, do you mean styles (Ctrl+Shift+Y)?
https://kinook.com/UltraRecall/Manua...tyledialog.htm