The sticky toolbar obstructs the inserted text when scrolling using Page Up/ Down in Source mode of the in-place WYSIWYG editor

Steps to reproduce

1. Create or go to a page with a lot of text (to have several screen views down)
2. Edit the page in-place
3. Click on "Source" button
4. Place the caret on the first top text line
5. Press Page Down
6. Type some text
7. Observe the inserted text

Expected results

After pressing Page Down, the caret is placed just below the sticky toolbar, so the text can be seen as it's being typed.

Actual results

After pressing Page Down, the caret is placed behind the sticky toolbar which is at the top of the editing area, so the typed text is not visible until it reaches the end of the bar.

It is to be mentioned that on Chrome and Edge on Source mode the view is advanced with one screen when pressing Page Up/ Down, but on Firefox the view is advanced all the way to the bottom (no intermediate screen scrolls, which is unexpected).

As a result, on this case, the typed text is obstructed by the bottom sticky toolbar which occupies the whole width of the editing area, so the user has to scroll down in order to see the typed text.

This behavior does not reproduce in Firefox if the page is edited in WYSIWYG mode (instead on Source), where the screen view is advanced one at a time.