Display "Click to add a cell" button as a part of notebook, not background

[andrii-i]

Problem

Currently "Click to add a cell" is rendered as a part of background / outer notebook area (grey in the JupyterLab light theme) under the drop shadow from the notebook / inner notebook area (white in the JupyterLab light theme).

To me it seems that the way how button is rendered in JupyterLab, as a part of notebook / inner notebook area (white in the JupyterLab light theme) is easier to read / parse. As an added bonus, this would make design language used in lab and notebook more consistent.

Notebook:

JupyterLab:

Proposed Solution

Render "Click to add a cell" button as a part of notebook / inner notebook area (white in the JupyterLab light theme).