The Agilitest editor is very particular, because it allows you to replay the tests and modify them at the same time, with the granularity of a simple action.
This allows you to go to the basics when it comes to changing a test or to maintain them, these activities are necessary to make live your test base, but obviously you must spend the least time to focus on the essentials: increase functional coverage or depth of your tests, do exploratory testing...
Step by step
Agilitest allows you to replay actions independently of each other. Just click the play button that appears at the top right of each activable action when you hover over it.

Play button at the right
Agilitest will then immediately perform this action on the tested software and return the result to you.

In this case, the element could not be located and the action failed: it is then necessary to modify the locator of the object if it still exists, or to modify the test more in depth.
This operating mode allows you to run your test step by step by successively selecting the actions one after the other and thus check the progress of each action.
It is also very powerful to set up the tested software in a context on which you know that you will be able to continue your test edition.
For example: click on a URL navigation to return to the launch of the page.
Breakpoints
The easiest way to modify an existing action or insert an action at a given location is to set a breakpoint.
To do this, simply click on the small STOP button at the top left of your action.

Then you run your test by clicking Play in the Channel Management tab.

The test will then run to the breakpoint and stop just before playing the action.

If you select the reduced mode execution in the channels management tab, the Agilitest editor will be reduced to let you better see what is happening in your application, it can be useful if you only have a single screen.

Whatever the selected execution mode, you just have to enter the capture mode to select a new component or recover the locator of the component causing a KO.

Then you can check that your action is going well step by step.

Java run mode
The step by step mode is a special mode dedicated to the editing / modification of tests. ATS has been designed to generate java code to run compiled tests, which is particularly suitable for launching continuous integration tests, or running full test campaigns in Agilitest. It is fast and efficient.