I don't know if breadcrumbs is the right word. It is all the little tabs showing the depth of the code i.e.: "Declaration", "Function", "Code Section", "Block", "Code Section", etc.

You move the cursor and they changed and shows where you are at that point.

VIDEO : https://i.imgur.com/VJVLoFo.mp4

That video shows what I meant. At the beginning I move the cursor with the mouse. It is fast and the redrawing is quick.
I go back to the starting point, and I move the cursor with the arrow keys (Keyboard). I move fast down and you can see the cursor stops, the breadcrumbs redrawing continues and then the cursor jumps to another line.

Can that performance improve?

Can you let me know the exact PL/SQL Developer version you are using?

Version:
PL/SQL Developer
Version 15.0.1.2051 (32 bit)

Okay. Can you send me the source file where this issue occurs, so that we can try to reproduce and fix this?

I sent you the code via private message

Thanks. I cannot immediately reproduce the issue, but we'll investigate.