Feature request: remember scroll position after tab change

**Is your feature request related to a problem? Please describe.**
When working with a big piece of text, I sometimes scroll down and copy some text into another tab. When switching back to the first tab, both the input and the output pane is back on top. So I don't know where I was working just now.

**Describe the solution you'd like**
After tab switching, scroll position should be remembered and it should not scroll back to top every time.

Start by tracing the tab-switching behavior and how the input and output panes are restored. Reproduce the issue with long text, switch tabs after scrolling both panes, and confirm that returning to the tab restores each pane's previous scroll position instead of moving to the top.

Written by the indexing model from the issue text.