Remove the user-mappable function and use commands instead.

autoload/vimwiki/base.vim

@@ -1101,8 +1101,10 @@ function! vimwiki#base#find_prev_link()
 endfunction
 
 
-" This is an API function, that is, remappable by the user. Don't change the signature.
-function! vimwiki#base#follow_link(split, reuse, move_cursor, ...)
+function! vimwiki#base#follow_link(split, ...)
+  let reuse_other_split_window = a:0 >= 1 ? a:1 : 0
+  let move_cursor_to_new_window = a:0 >= 2 ? a:2 : 1
+
   " Parse link at cursor and pass to VimwikiLinkHandler, or failing that, the
   " default open_link handler
 
@@ -1138,7 +1140,7 @@ function! vimwiki#base#follow_link(split, reuse, move_cursor, ...)
 
     " if we want to and can reuse a split window, jump to that window and open
     " the new file there
-    if (a:split ==# 'hsplit' || a:split ==# 'vsplit') && a:reuse
+    if (a:split ==# 'hsplit' || a:split ==# 'vsplit') && reuse_other_split_window
       let previous_window_nr = winnr('#')
       if previous_window_nr > 0 && previous_window_nr != winnr()
         execute previous_window_nr . 'wincmd w'
@@ -1162,7 +1164,7 @@ function! vimwiki#base#follow_link(split, reuse, move_cursor, ...)
 
     call vimwiki#base#open_link(cmd, lnk)
 
-    if !a:move_cursor
+    if !move_cursor_to_new_window
       if (a:split ==# 'hsplit' || a:split ==# 'vsplit')
         execute 'wincmd p'
       elseif a:split ==# 'tab'
@@ -1171,8 +1173,8 @@ function! vimwiki#base#follow_link(split, reuse, move_cursor, ...)
     endif
 
   else
-    if a:0 > 0
-      execute "normal! ".a:1
+    if a:0 >= 3
+      execute "normal! ".a:3
     else
       call vimwiki#base#normalize_link(0)
     endif

doc/vimwiki.txt

@@ -677,12 +677,24 @@ Vimwiki file.
 *:VimwikiGoBackLink*
     Go back to the wiki page you came from.
 
-*:VimwikiSplitLink*
+*:VimwikiSplitLink* [reuse] [move_cursor]
     Split and follow wiki link (create target wiki page if needed).
 
-*:VimwikiVSplitLink*
+    If the argument 'reuse' is given and nonzero, the link is opened in a
+    possibly existing split window instead of making a new split.
+
+    If 'move_cursor' is given and nonzero, the cursor moves to the window with
+    the opened link, otherwise, it stays in the window with the link.
+
+*:VimwikiVSplitLink* [reuse] [move_cursor]
     Vertical split and follow wiki link (create target wiki page if needed).
 
+    If the argument 'reuse' is given and nonzero, the link is opened in a
+    possibly existing split window instead of making a new split.
+
+    If 'move_cursor' is given and nonzero, the cursor moves to the window with
+    the opened link, otherwise, it stays in the window with the link.
+
 *:VimwikiTabnewLink*
     Follow wiki link in a new tab (create target wiki page if needed).
 
@@ -829,35 +841,6 @@ Vimwiki file.
     are specified, outputs all tags.  To make this command work properly, make
     sure the tags have been built (see |vimwiki-build-tags|).
 
-------------------------------------------------------------------------------
-4.3. Functions                                              *vimwiki-functions*
-
-Functions to interact with Vimwiki. (It's intended that most commands will be
-replaced with corresponding function calls in the future.)
-Warning: this is currently unstable and likely to change.
-
-
-To map them to a key, use >
- nnoremap <C-K> :call vimwiki#base#function_name(arg1, arg2)<CR>
-<
-
-                                                          *vimwiki-follow_link*
-vimwiki#base#follow_link({split}, {reuse}, {move_cursor})
-    Open the link under the cursor. {split} can have the following values:
-        'nosplit'       open the link in the current window
-        'vsplit'        open in a vertically split window
-        'hsplit'        open in a horizontally split window
-        'tab'           open in a new tab
-
-    If {reuse} is 1 and {split} one of 'vsplit' or 'hsplit', open the link in
-    a possibly existing split window instead of making a new split.
-
-    If {move_cursor} is 1 the cursor moves to the window or tab with the
-    opened link, otherwise, it stays in the window or tab with the link.
-
-    For example, <CR> is per default mapped to
-    vimwiki#base#follow_link('nosplit', 0, 1)
-
 
 ==============================================================================
 5. Wiki syntax                                                *vimwiki-syntax*

ftplugin/vimwiki.vim

@@ -259,8 +259,8 @@ command! -buffer VimwikiDeleteLink call vimwiki#base#delete_link()
 command! -buffer VimwikiRenameLink call vimwiki#base#rename_link()
 command! -buffer VimwikiFollowLink call vimwiki#base#follow_link('nosplit', 0, 1)
 command! -buffer VimwikiGoBackLink call vimwiki#base#go_back_link()
-command! -buffer VimwikiSplitLink call vimwiki#base#follow_link('hsplit', 0, 1)
-command! -buffer VimwikiVSplitLink call vimwiki#base#follow_link('vsplit', 0, 1)
+command! -buffer -nargs=* VimwikiSplitLink call vimwiki#base#follow_link('hsplit', <f-args>)
+command! -buffer -nargs=* VimwikiVSplitLink call vimwiki#base#follow_link('vsplit', <f-args>)
 
 command! -buffer -nargs=? VimwikiNormalizeLink call vimwiki#base#normalize_link(<f-args>)