Set indent width (for increase and decrease indent) to 2.

Added markdown word wrap which I don't think actually works.
Defined select all usermode control.
Set up divider for max line width.

programs/kakoune.nix

@@ -8,13 +8,29 @@
       enable = true;
       highlightCursor = true;
     };
-    hooks = [{
+    indentWidth = 2;
+    hooks = [
+        {
           # When the filetype=latex option is set in a buffer context (automatically), add a new hook to build the latex file on write
           name = "BufSetOption";
           option = "filetype=latex";
           commands = "hook buffer BufWritePost .* %{ texlab-build }";
-    }];
+        }
+        {
+          # When the filetype=markdown option is set (automatically), set word wrap on
+          name = "BufSetOption";
+          option = "filetype=markdown";
+          commands = "add-highlighter buffer wrap -word";
+        }
+    ];
     keyMappings = [
+      # Define select all
+      {
+        key = "a";
+        mode = "user";
+        effect = "*%s<ret>";
+        docstring = "Select all";
+      }
       # Define usermode yank/copy and paste
       {
         key = "y";
@@ -39,6 +55,9 @@
 
     # don't remove trailing indent
     set global disabled_hooks .*-trim-indent
+    source ${pkgs.writeText "kakoune-divider.kak" (builtins.readFile ./kakoune/divider.kak)}
+    set-option global divider_face LineNumbers
+    divider-on 80
 
     eval %sh{kak-lsp --kakoune -s $kak_session}
     lsp-enable

programs/kakoune/divider.kak

@@ -0,0 +1,46 @@
+# A script for long-line coloring.
+
+# We use almr's looping techniques, as described in:
+
+# https://discuss.kakoune.com/t/kakscript-has-loop-catch-this-head-tail-shift-int-0-streq-etc/1885
+# https://gitlab.com/kstr0k/sel-editor.kak/-/snippets/2178452
+
+declare-option -docstring 'divider pane coloring' \
+str divider_face 'default,rgb:dae3e6'
+
+declare-option -hidden int divider_column
+
+define-command -params 1 -docstring 'divider-on <column>: colorize right side starting from column' \
+divider-on %{
+    add-highlighter -override window/divider group
+    set-option window divider_column %arg(1)
+    divider-do-256 divider-colorize
+} -override
+
+define-command -docstring 'divider-off: remove right-side coloring' \
+divider-off %{
+    remove-highlighter window/divider
+} -override
+
+define-command -hidden -params .. divider-do-2 %{
+    %arg(@)
+    %arg(@)
+} -override
+
+define-command -hidden -params .. divider-do-4 %{
+    divider-do-2 divider-do-2 %arg(@)
+} -override
+
+define-command -hidden -params .. divider-do-16 %{
+    divider-do-4 divider-do-4 %arg(@)
+} -override
+
+define-command -hidden -params .. divider-do-256 %{
+    divider-do-16 divider-do-16 %arg(@)
+} -override
+
+define-command -hidden divider-colorize %{
+    add-highlighter "window/divider/%opt(divider_column)" column %opt(divider_column) %opt(divider_face)
+    set-option -add window divider_column 1
+} -override
+