There are likely very few users which means that more or less use cases are not tested. This means greater probability of issues.
To use this addon, tether braille to review in NVDA settings Braille category. You likely want also that review cursor follows system caret most of time (see NVDA settings Review Cursor category). Selection is shown in edit controls and documents with dots 7 and 8 when "Show selection" is enabled in NVDA settings Braille category. When braille is tethered to review and review follows caret, review cursor is positioned to end of selected text when selection changes so you can see immediately how it changed.
You can easily see what you have selected for example for copying or formatting in text editor. You can move around edit control or document with braille gestures and text review commands which move braille display. Movement does not affect on caret, and it is not restricted to selected text. It means that you can investigate both selected and unselected part of text with braille. You can use routing buttons to move review position and/or caret according to NVDA Braille category "Move system caret when routing review cursor" setting.
If "Show selection" is disabled, review cursor is positioned to end of selected text when braille is tethered to review, review follows caret and selection changes.
To see selection outside of edit controls, browse mode should be used where supported.