A variety of methods are at your disposal
There are some very useful commands listed here, most notably [I, which will display all lines in the current and all included files containing the keyword under the cursor. See :h [I and :h include-search.
You can :grep or :vimgrep to search for occurrences of a particular symbol (or any pattern for that matter), ...
Vim comes with a complete set of commands and options for using tags. You can read all about it in :help tags (the generic stuff) and :help ctags (the ctags-specific stuff that also applies to jsctags).
But your plugin doesn't use any of those commands and settings and don't even use an actual tags file so you have an hyper-specialized plugin and a built-in ...
You can use a FileType autocmd and map those keys to <Nop>:
autocmd FileType tagbar nnoremap <buffer> H <Nop>
autocmd FileType tagbar nnoremap <buffer> L <Nop>
Also always remember to enclose your autocmds with a augroup.
Function name should start from capital letter
nmap <F9> :TagbarToggle<CR> :exec Adjust_tagbar_width() <CR>
Consulting the documentation of these plugins, you can find out how to tweak the position of their buffers. I achieved what you want as follows:
let g:tagbar_left = 1
let g:tagbar_vertical = 25
let NERDTreeWinPos = 'left'
nnoremap <f5> :NERDTreeToggle <CR> :TagbarToggle <CR>
Note: :NERDTreeTabsToggle is not part of NERDTree itself, as it ...
You can use |. See :help :bar:
'|' can be used to separate commands, so you can give multiple commands in one line. If you want to use '|' in an argument, precede it with '\'.
In your case it would be:
nnoremap <f5> :NERDTreeTabsToggle | :TagbarToggle<cr>
You should check your current directory to see if its the same as your tags file
If not just
and try again using tags.
Please check this response for ways to set searching directories for tag files
Here's my git repo which should be most up to date:
And here are the rules I use as of writing this post: