GSOC 2020: [Preferences] Button problem in Preferences #9185

[yzykov]

[Preferences] Button problem in Preferences #9185

1. The following fix adds a tool-tip to the "new Window" button in preferences.
   The tool tip uses an existing sentence, which explains what the new pop-up window is used for.

It is less descriptive, but it requires no changes in reference files => no translation needed

I will create another pull request with more descriptive pop-up, but which will require translation to be done.

Tested on Linux & Windows

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