Some quick thoughts
1) The evaluation symbols have a problem in my pc. I think you use fonts, and they dont show well in some non-latin bases windows versions
I dont see the unclear symbol and the += symbol misses the - from the +
2) One thing that i surely miss is subtags. At least one two levels more
3) Copy - paste method, copies moves but not the structure (variations + tags). So when you want to move-copy an opening you have to recreate the whole structure (at least i did not find a way to do it)
4) It would be nice to comment with arrows, squares , circles over the board. Some times they tell much more than a lot of words
5) One click expand-collapse for variations-subvariations. They always open expanded and you might want to save space.
6) It would be good if import-export to pgn supported the structure one created for the opening (variations-subvariations)
For example a comment of the type #2..e6# would mean that everything from now on is under variation 2...e6
if somewhere down the line i have ##5.f4## it means that everything after that is under the subvariation (which is a child of the previous parent)
Not hard and can support recursively as many nested steps you like just counting the #
That way , importing - exporting would not lose the structure.