I don't know the difference between those two Maple 2020 icons - I suspect it is none. But your question reminds me of one of the most useful Maple's features that is somehow hidden: having one worksheet open, you can open another worksheet
- either sharing the kernel with the open one, or with an entirely new kernel
- either as a tab or in a new window - even put the two windows side by side
So what is this 'kernel' business about? The word, unfortunately, means nothing to me, but translates to this: when you have two worksheets sharing the kernel, it means the computations you do in one of them are active in the other one; e.g. you assign A := 1, go to the other worksheet, input A, and the output is 1. Not sharing the kernel means, naturally, the opposite: computations done in each worksheet are entirely independent, not shared.
Sharing the computations done in two or more worksheets allows for quick drafting (on a second worksheet) without messing around with the text and formulas developed in the first worksheet (the main line of thoughts). It is advantageous.
Not sharing the computations among some worksheets is also extremely useful: It allows for experimentation without changing any results obtained in the first (main) worksheet.
Depending on the context, sometimes sharing, sometimes not sharing, is the way to go. Moreover, having one worksheet open, you can have several other ones sharing the computations, and at the same time several other ones not sharing computations with any other one. For each new worksheet, you can choose whether to share or not the computations with any other open worksheet.
And how do you have access to this (for me, fantastic) feature? Open the Maple preferences pane and, in General, where you see "How should Maple handle the creation of a new Math Engine?, choose "Ask each time a new document is created."
The other feature is about opening new worksheets in tabs or new windows. The default is tabs, but windows is also handy: you can put two worksheets side by side and compare the computational flow, sharing, or not, the kernel (computations). To have two worksheets open in two windows (sharing or not the computations), you can: a) in the preferences, Interface > Open worksheets in: choose "New Window" instead of "New Tab"; or b) keep the default of opening in tabs, then right-click a tab and choose "Open tab in a new window".
To summarize, given two worksheets open, you have four options: have them in tabs or separate windows, and share or not the computations. Somehow, few people are aware of that, a concretely useful feature.
Edgardo S. Cheb-Terrab
Physics, Differential Equations and Mathematical Functions, Maplesoft