and workaround is that login to clamshell device, change the shelt to bototm,
then log back in to the tablet mode device.

warx@, maybe the right person to ask?

I don't know who added this behavior. IIRC, it is added before M-62.

The shelf should always be on the bottom in tablet. +Sammie who wrote that logic.
Manu, can you have a look at that as a starting project for shelf work? Sammie can give you pointers.

Sorry to bring this back from the dead, but can someone explain *why* the shelf should be on the bottom in tablet mode? Why should it not be a configurable option *regardless* of device orientation?

I often use my device in landscape tablet mode and it's incredibly annoying to have the shelf on the bottom vs. the left where I would prefer.

Version 64.0.3282.167 (Official Build) (64-bit) Acer Chromebook
Tablet mode, I always had the shelf on the right,now after the recent update my shelf stays at the bottom ( unless using keyboard)
Tablet/portrait ,shelf positions is greyed out
Tablet/landscape ,shelf position is greyed out.
Tablet/keyboard use  ,shelf position choices are available,right is chosen and is on the right.

Since research reveals that many Chromebook users have been adversely affected by the Chrome OS development team's decision to force the shelf to be in 'Bottom' position in Tablet Mode (and in Tent and Entertainment modes, too), I have compiled a comprehensive campaigning Issue Report, asking the Chrome OS development to undo this regressive, freedom-limiting restriction, by restoring our 'Left' and 'Right' shelf position options to Chrome OS Tablet Mode:

● 'Prior Tablet Mode Shelf Position "Bug Fix" Seriously Degrades Chromebook UX', 03 Mar 2018
» https://bugs.chromium.org/p/chromium/issues/detail?id=818423
— contains links to six related Issue Reports, and copies of 12 other end user complaints regarding the detrimental effects of restricting shelf position in Tablet & Tent & Entertainment Modes to 'Bottom' only.

If you too would appreciate the restoration of the 'Left' and 'Right' shelf position options to Tablet & Tent & Entertainment Modes, then please:
1. click on the link above,
2. scroll down to the bottom of the Issue Report webpage, and
3. click on the star, to 'Vote for this issue and get email change notifications';
4. optionally, do please also add a comment of your own, maybe describing how the new, forced, 'Bottom'-only shelf position imposition adversely affects your own use of Chrome OS.

Thanks in advance for your help in restoring user-determined shelf position freedom to Chrome OS Tablet Mode.

See also:

● 'Why Can I No Longer Choose Shelf Position in Tablet Mode?', 01 Mar 2018
» https://productforums.google.com/forum/#!topic/pixelbook/8XXiGakpREA
— an issue discussion thread in the Google Product Forums.

Received an update ,Version 64.0.3282.190 (Official Build) (64-bit) but shelf issue still present

Thank you for all your feedback, I care deeply about it, I'd like to track it in a clean single bug.

My thanks to omrilio@chromium.org for consolidating the nine Chrome OS Tablet Mode shelf-related issue trackers which I identified (plus my own) into a new meta-issue-tracker:
● 'Investigate improvements to shelf on tablet mode', 09 Mar 2018
» https://bugs.chromium.org/p/chromium/issues/detail?id=820368

If, like me and many other Chromebook users, you too would appreciate the restoration of the 'Left' and 'Right' shelf position options to Tablet & Tent & Entertainment Modes, or if you are experiencing other Tablet Mode shelf-related problems, then please:
1. click on the link above,
2. scroll down to the bottom of omrilio's Meta-Issue-Tracker webpage, and
3. click on the star, to 'Vote for this issue and get email change notifications';
4. optionally, do please also add a comment of your own, maybe describing how the new, forced, 'Bottom'-only shelf position imposition adversely affects your own use of Chrome OS, or supplying additional useful diagnostic info, such as specific details about how use of a particular app is hindered by the shelf.

Thanks in advance for your help in restoring user-determined shelf position freedom to Chrome OS Tablet Mode.

See also:

● 'Why Can I No Longer Choose Shelf Position in Tablet Mode?'
— an issue discussion thread in the Google Product Forums, 01 Mar 2018
» https://productforums.google.com/forum/#!topic/pixelbook/8XXiGakpREA

● 'Chrome OS: Tablet Mode Shelf-Related Issue Trackers'
– shared Google Sheets spreadsheet, 11 Mar 2018
» https://docs.google.com/spreadsheets/d/16XSTb96nJlWYlOhs3dPlLqiCdll4vdM1yxVZHMvCt3M/edit?usp=sharing