Explanation
When using a dynamic selector, the data type that is supported is String. A dynamic selector is a selector that uses a variable or an argument as a property for the attribute of the target element. This allows the selector to easily identify the target element based on the value of the variable or argument, and not an exact string, which might change depending on the interactions inside the automation project1. The variable or argument that is used in the dynamic selector must be of type String, as the attribute values are always strings2. For example, a dynamic selector can use a variable named MenuOption to click on different menu items in an application, such as File, Edit, or Format. The variable MenuOption must be a String variable, and its value can be changed at runtime to interact with different elements. A dynamic selector has the following format, where {
{Value}} is the name of the variable or argument that holds the property of the element you want to interact with1:
Dynamic Selector Format <tag attribute = { {Value}} />
References: Dynamic Selectors and How many types of selectors are in UiPath? from UiPath documentation and forum.