chore(kb/zen): revise article

knowledge base/zen browser.md

@@ -15,9 +15,10 @@ brew install --cask 'zen-browser'
 
 </details>
 
-Split tabs by:
+<details>
+  <summary>Split tabs</summary>
 
-1. Selecting desired ones:
+1. Select the desired ones:
    - Hold `CTRL` or `CMD`, then left-click to select only specific tabs, or
    - Left-click 2 tabs while holding the Shift key to select all tabs in between.
 1. Right click one of the selected tabs.
@@ -27,15 +28,28 @@ Split tabs by:
 The default Split View layout is a grid. Change it by pressing the 🔗 button in the top address bar (usually between the
 tab container indicator and the favourites' star button).
 
+</details>
+
+<details>
+  <summary>Reduce the window's border</summary>
+
+1. Go to `about:config`.
+1. Look for `zen.theme.content-element-separation`.
+1. Set the padding value to whatever one wants.<br/>
+   Defaults to `8`.
+
+</details>
+
 ## Further readings
 
 - [Website]
-- [Main repository]
+- [Codebase]
 - [Documentation]
 
 ### Sources
 
 - [How do I use the Split View feature?]
+- [Reduce Window Border Thickness]
 
 <!--
   Reference
@@ -43,7 +57,8 @@ tab container indicator and the favourites' star button).
   -->
 
 <!-- Upstream -->
-[documentation]: https://docs.zen-browser.app/
-[how do i use the split view feature?]: https://docs.zen-browser.app/faq#how-do-i-use-the-split-view-feature
-[main repository]: https://github.com/zen-browser/desktop
-[website]: https://zen-browser.app/
+[Codebase]: https://github.com/zen-browser/desktop
+[Documentation]: https://docs.zen-browser.app/
+[How do i use the split view feature?]: https://docs.zen-browser.app/faq#how-do-i-use-the-split-view-feature
+[Reduce Window Border Thickness]: https://github.com/zen-browser/desktop/discussions/3452#discussioncomment-13363156
+[Website]: https://zen-browser.app/