Форум поддержки Thunderbird

I want to customize shortcuts in Thunderbird using tbkeys but I can't find the right command name.

In the description is written: "Most command names can be found in the main command set file of the Thunderbird source code."

But where I can found all/ more/ other command names?

In my case I want to change:

• "Move to previous UI element" (default: Shift + Tab)
• "Move to next main UI area" (default: F6)

listed in this overview

In the attached screen shot they are two type of folders - One is yellow and looks like a paper folder and the others are rectangular in shape in different colors (here in res and purple) . I am unable to delete the rectangular folder that appear permanent and I don't even know how it was created as I used the same command "new folder" under the inbox or "new subfolder" under a yellow folder - I hope that this is clear : I want to delete the rectangular folders when needed