If either of these features is already present in PyCharm, please excuse me. I did what I think is a reasonable amount of research before posting here.
What I would like is the ability to lock/unlock, or synchronize/un-synchronize if you will, the scrolling of two adjacent editor tabs at their current position. The tabs need not have the same file loaded, but could have. In fact, it is the 'same file' case that I am most interested in.
I have found the 'Compare with Clipboard' feature, and that works ok I guess. IMHO, what would work better would be a 'Compare Selected' feature that compared the selected text in multiple tabs without having to first copy one of those selections to the clipboard. With that functionality in place, a scroll lock (especially a vertical scroll lock on a vertically split file) would be a complimentary feature, making it easier to get the two chunks of the file that need to be compared into view at the same time so that they can be selected.
This is a common need when refactoring poorly written legacy code that has been copy-and-pasted-and-hacked multiple times within the same module.