I did experiment and select convex concave vertex, but… it seems more difficult than I think 
Many case it selected wrong vertices !
The follow methods
I will try and test to see if it works well 
Hey friends! Can you help me and give me rating on gumroad ? 
I really need some stars 
Done! Five stars! It deserves it! 
As to the vertex corner selection: there is already a tiny addon made by someone (I do not remember his name now) that makes a selection of vertexes by the number of the edges connected with them, it does some work but it selects some kinds of corners that have not to be selected too.
I mean I know where is the difficulty you met. But there is the challenge also: finding a way to overcome the impediment.
Anyway, just keep it in mind… there can occur a related mind flash in the future…
Thanks so much!! 
Yes, I am interested to this sharp vertex selection problem too.
I will do some experiment later 
Now I am working on the GM vertex mode thing
I gave you 6 out of 5 stars 
Ohh! I am so glad to hear that, thank you 
I just updated !!
Version 1.9.2:
Now you can set the hint text’s X-position on the screen (in addon’s preference setting).
You can enter the offset value from the left of the screen.
Now Vertex mode is supported !!
You can select a vertex to run the tool ! (Use the vertex’s normal)
Also, you can select 2 vertices to run, it will align on the line between 2 vertices.
And you can select 3 vertices too, it will align on the virtual plane formed by 3 vertices.
(more than 3 is ok, but it only use the first 3 )
Enjoy 
4 stars because I’m evil. 
I love to see and play with this as it evolves.
Thanks a lot!!!
You are welcome
No problem. I will try to make it to a good program.
Because developing good software is my personal interest.
Hi Kushiro. 
Thank you for creating this add-on.
It is very helpful because it is difficult to manipulate meshes using Grid in existing Blender operations.
It is the one who used gridmodeler for a few months, but I would like to give you feedback because I thought that it would become easier to use if I could change some functions by each individual.
1, It is a convenient hint at the bottom left of the screen, but I want the key operation or check column that can switch the display and non-display in the menu of the add-on and the 3D view when gridmodeler is used.
The text size is reduced and hidden at present, but this is inconvenient.
3, In the mode of gridmodeler, I can’t understand what the existing mode is unless I see the character display at the bottom right of the screen or check the status with the click of the mouse.
It is easy to understand what mode I am in now by using icons other than text to know what mode I am in. Also, if you concentrate too much information on the bottom right corner of the screen, it will be hard to understand.
5、I want to change the color of the text of the useful hints at the bottom left of the screen.
The current color of the text is hard to see for people with bright theme colors.
Hi.
Maybe you could take a look at the source code of Flexi Bezier Utilities : Flexi Bezier Tool
It features an Hotkeys Overlay (in the bottom left corner) but the user can change its location, the font size and there is also some code to make the overlay only appear on the biggest viewport.
Thank you for the feedback
It seems that the hint text and UI should be re-designed. It is hard to add too much setting in the preference, so may be I should make a better UI display.
The key will be configurable, but I need to find the code for preference screen.
I see. I will take a look later when free.
Spaceship 
Simple tutorial for Grid Modeler
Friday’s spaceship
