Unable to reproduce the issue on Win-10 using chrome reported version #63.0.3239.84 and latest canary #65.0.3294.3.

Attached a screen cast for reference.

Following are the steps followed to reproduce the issue.
------------
1. Opened bookmark Manager
2. Shrinked right side to view left side bookmarks that cascade off to the right. 
3. Able to view the bookmarks as expected.

reporter@ - Could you please check the screen cast and please let us know if anything missed from our side. Also please check the issue on latest canary #65.0.3294.3 by creating a new profile without any apps and extensions and please let us know if the issue still persist or not.

Thanks...!!

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Screenshot shows left side bookmarks that cascade off to the right that go beyond where I can shrink or expand the view to see those bookmarks. I was always able to do this before. The colors changed also.

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Thank you for providing more feedback. Adding requester "krajshree@chromium.org" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

"Unable to reproduce the issue on reported chrome version 63.0.3239.84 and on the latest canary 65.0.3297.0 using Windows 10 with the below mentioned steps.
1. Launched Chrome
2. Opened Bookmark manager
We are able to see the bookmarks with out any issue. Attachng the screen cast of the same.

@Reporter: Could you please let us know whether we have missed any steps while reproducing the issue.

Thanks! "

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None of these screen recordings show what my problem is. I can do what is shown - enlarging the right side - what I can't do is enlarge the left side to see all the bookmarks that cascade off to the right. It only goes halfway, no further. If I did the screen recording correctly  you can see I'm limited in viewing bookmarks. What ever changes were made do not allow me to view these bookmarks as I was in the past. 

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Thank you for providing more feedback. Adding requester "vamshi.kommuri@techmahindra.com" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Able to reproduce this issue on Windows 10, Mac OS 10.12.6 and Ubuntu 14.04 using the latest Canary 65.0.3298.3 and Stable 63.0.3239.108 by following the steps shown in comment #6.

This is a Non-Regression issue as this is observed from M62 chrome builds from introduction of Material Design on Bookmarks. 
Hence marking this as 'Untriaged' for further updates from Dev.

Thanks..

+calamity

The video in #6 is the extreme case, where the sidebar is at its max width but there are still invisible bookmarks in the tree.

Maybe it's possible to remove the `overflow: hidden` style from #folder-label nodes past a certain depth? (like, 3? 4?) That way, there'll be no scrollbar until you reach a certain depth. Or is that overcomplicating the solution?

 Issue 797691  has been merged into this issue.

 Issue 793972  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/07131e1caad858f9037fadc83a45a1894170d095

commit 07131e1caad858f9037fadc83a45a1894170d095
Author: Christopher Lam <calamity@chromium.org>
Date: Tue Jan 09 03:16:38 2018

[MD Bookmarks] Make sidebar scrollable horizontally.

This CL makes the sidebar scrollable so that users can see deeply nested
folders. It also makes the general app element unscrollable so that
we never double up on scroll bars.

Bug:  794572 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I413e54f03f42bb3f2cdb6ca52dee77c09794abc6
Reviewed-on: https://chromium-review.googlesource.com/851394
Reviewed-by: Tim Sergeant <tsergeant@chromium.org>
Commit-Queue: calamity <calamity@chromium.org>
Cr-Commit-Position: refs/heads/master@{#527885}
[modify] https://crrev.com/07131e1caad858f9037fadc83a45a1894170d095/chrome/browser/resources/md_bookmarks/app.html
[modify] https://crrev.com/07131e1caad858f9037fadc83a45a1894170d095/chrome/browser/resources/md_bookmarks/folder_node.html
[modify] https://crrev.com/07131e1caad858f9037fadc83a45a1894170d095/chrome/browser/resources/md_bookmarks/item.html
[modify] https://crrev.com/07131e1caad858f9037fadc83a45a1894170d095/chrome/browser/resources/md_bookmarks/list.html

Thanks to everyone helping with this issue. Unfortunately issue remains for me. I can not expand the left side of bookmark page to see all  bookmarks.

This will reach Canary in the next couple of days, but won't hit Stable until March unfortunately. Beta will release in February.

As a workaround, you can press F12, then go to the Console tab and paste in

Array.prototype.map.call($$('* /deep/ div#folder-label'), x=>x.style.overflow = 'initial'); $$('* /deep/ #sidebar')[0].style.overflow = 'auto'

This will only work while you leave the bookmark manager open, it will reset next time.

Verified the fix on Mac 10.12.6, Win-10 and Ubuntu 14.04 using latest Chrome version #65.0.3317.0 as per the comment #6 and #12.
Attaching screen cast for reference.
Observed that side horizontal scrollbar is added to bookmark manager so that users can see deeply nested folders.
Hence, the fix is working as expected. 
Adding the verified labels.

Thanks...!!

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The general problem is also, that the MD bookmark manager wastes too much space, so that one can see far less, compared with the previous bookmark manager design. It would be great, when you would reduce the space between 
- the arrow and the folder symbol,
- the folder symbol and the folder name.

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I hope this means the issue is still being worked on. The problem persists for me. 

This issue is closed. I don't think the spacing is going to change. The horizontal scrollbar will be in the latest canary. Stable will be in roughly 6 weeks.

This is another case where something which was working perfectly fine has been changed to "look nice" and introduced many other problems at the same time, killing or severely hampering workflow in a serious business environment. 

@vorak
As you can see, there is no interest to take this further. I advise you to use Firefox Quantum if you rely on bookmarks. I have switched and the Bookmark manager there is far superior to what you will get in Chrome. Also the import worked without any hassles. As I'm using bookmarks extensively to source products for my business, I'll take functionality over "beautification" any time of the day.