Show buffer outline (e.g. symbols from LSP)

[yatesco]

Hi there! In emacs I use imenu a ton. It provides a list of symbols in the current buffer. Is there an equivalent in ALE?

The help mentions

g:ale_update_tagstack                                   *g:ale_update_tagstack*
                                                        *b:ale_update_tagstack*
  Type: |Number|
  Default: `1`

  This option can be set to disable updating Vim's |tagstack| automatically.

which made me think I could use vim's tags functionality (and FZF :Tags), but it's empty and prompts to generate a tags file. echo ale_update_tagstack shows E121: Undefined variable: ale_update_tagstack, so I wonder whether the documentation is stale?

Thanks :-)