I want to add a Millis timer in place of a for loop

[StefanL38]

The standard blink without delay-example code makes it unnescessary complicated to understand non-blocking timing.

The main reason is that this example and other tutorials do not focus on the fundamental difference how non-blocking timing works.

You should learn the principle prior to looking into the code.
Knowing the basic principle will make it much easier to understand the code

I recommend a version that puts the details about non-blocking timing into a function
that can be used in a single if-condition that says what the function is doing

checking if TimePeriodIsOver()

if( TimePeriodIsOver(myTimingVariable,Period)  ) {
  // do timed action
}

Example-code for timing based on millis() easier to understand through the use of example-numbers / avoiding delay()

non-blocking timing. Execute code only from time to time. There are a lot of different ways to learn programming. This thread wants to add another approach that is different to the yet existing ones. UPDATE 06.01.2023 if you are mainly interested in applying non-blocking timing you can do a quick read of this short tutorial / demonstration If you are intersted in understanding the details how it works go on reading here. I use an everyday analogon in this post to explain the basic principle …

best regards Stefan