Here is what I'm doing in version 6.0.5 to simulate the old tag view style:
Create an arbitrary tag with a . prefix so that it is near the top of your main a-z tag list. This will mean either right-clicking on the Tag icon and selecting "Create tag ..." or right-clicking your main a-z parent tag and selecting "Create tag in .evaluate ..."
Since I had dumped my tags into a parent tag, I'm using .evaluate in these examples.
Right-click .evaluate and select "Create tag in .evaluate ..." (if not using a parent tag, just click on the Tag icon as stated above)
Create the tag a.aaa (the period might help bring the new tag to the top of your list of tags beginning with the letter "a".)
Click on the first tag that begins with the letter "a"
Scroll down to the last tag that begins with the letter "a"
Hold the shift button down and click on the last tag
Let both mouse and keyboard keys go
Scroll back to the first tag
Click-and-Drag the highlighted group until the cursor is directly over the new a.aaa tag
Drop the tags into their new parent
Click the little triangle to the left of the a.aaa tag, to collapse the list
Repeat all these steps for tags b.bbb through z.zzz
As you were building this, you will have noticed that the Note List displays only the tags in the letter grouping. (If you don't see the Note List, press F11)
This technique may not get you 100% simulation (such as scrolling) but it certainly makes it more simple to move tags to different parents without interminable scrolling through the leftmost column.