Improve editing of saved sessions to remove saved pages

[alterechtschreibung]

First of all, thank you for implementing a way to modify the saved sessions. That's a good start.
Unfortunately the current way has the following drawbacks:

• If you accidentally delete the wrong page you lose important tabs.
• It is very time consuming and slow to delete a huge chunk of tabs.
• It is not possible to just deselect some tabs and open the other tabs (without really modifying the saved session)

A more elegant way to modify the saved session would be:
Add check-boxes preferably on the left side. When you open the list, all check-boxes are checked.
You can deselect tabs by unchecking the checkbox.
When you click on the open button, only the selected/checked tabs will be opened.
Add another button "save changes" to delete the unchecked/deselected tabs.

[alterechtschreibung]

I made a mock-up.