Change the type of the input parameter from String to Object, and select the object that is the context object for your button (in other words, that 'surrounds' you button and is available on the page).
Using this object you can check the value of the attribute that is part of the object you pass to the microflow.
Also, you can check out the Mendix Learning modules: they contain these topics and make sure you don;t get stuck all the time while taking your first steps in Mendix :)
Wieke Bouten, thank you. It's help me.
I create new entity and set it as data source for data view. Now I have message
'The selected page 'Page' expects an object of type 'Entity' and cannot be used as a home page. Change the page or use a microflow to provide the page with an object.
Why I can't use created entity in home page? What ways exist for a solution ?