gvim - How to jump to the definition (declaration) of a custom function when editing a vimrc file in vim?

Question

When editing a vimrc file in vim, what shortcut key can be pressed to jump from the place where a custom function (written by vimscript) is called to the place where the custom function is defined (declared)? Is there any shortcut key without installing a plug-in like ctags? Note that pressing K (ie shift+k) can only jump to the description of the system function.

Answer 1

Plug-in must be installed, not supported.
In the same file, you can try *, # signs. No guarantee it will be found, but it will work.