Hello @Bozhidar743 .
Dynamic selector is a selector defined inside a desktop flow, which is intended to interact with a specific UI element, even if the selector of the UI element might change between flow executions.
For that purpose, Power Automate Desktop offers the capability to the user to use operators inside the Selector builder, for making dynamic the value that a attribute of the selector can take. More information can be found here: Build a custom selector - Power Automate | Microsoft Docs
For your case though, you probably have to create a loop with variable that would take incremental values. I suspect the selector for the UI elements you would like to interact with would be of the format:
First UI element: html > body > div > table > tbody > tr:eq(0) > td:eq(0)
Second UI element: html > body > div > table > tbody > tr:eq(1) > td:eq(0)
Third UI element: html > body > div > table > tbody > tr:eq(2) > td:eq(0)
As you may observe, the 'tr:eq(x)' is dynamic, it changes for each element while the rest of the selector remains the same. Therefore, you have to replace the number inside with a variable (lets say 'x') that would start from 0 and goes up to the number of elements-1. The selector defined inside the 'Extract data from web' action should be something like: html > body > div > table > tbody > tr:eq(%x%) > td:eq(0).