[Disturbing Theme in Cura 5 - is it possible apply custom theme to make like 4?]

These don't seem to work, so I simply went back to 4.13.1.

[What causes these feed rate variations?]

Ok, never mind, it was Print Cooling > Minimum Layer Time.

[What causes these feed rate variations?]

Here's a feedrate preview of a 20mm calibration cube I sliced:

 

 

Here are my speed settings (based on a fresh "Normal" profile):

 

 

I expected the cube to basically have one single color in the feedrate preview. Why doesn't it?

 

For context, I am investigating this because in my print I have some layer shifts that I ascribe to speed changes:

 

(This print was with different settings.)