Unfortunately there's no simple answer to your question. It depends on exactly what Find Expression Test Studio put together for locating that element. There are probably a thousand different ways for locating the same element within the DOM, even with DOM that doesn't change. There's by tag index, by text content, by path, etc. We have to study the specific find expression for a specific element to know exactly how fragile it may be.
You do risk the reliability of the test automation when you do not have unique ID's or names attached to the elements. We realize there are cases this is not possible, especially if you're using third party controls on your web page. In such cases we recommend adding unique ID's to the complex control (e.g. a calendar popup) such that we can use that in a "chained expression". A chained expression means find element A (the one with the unique ID) then find element B underneath it, possibly by text content or tag index or whatever we can determine is going to be the most reliable. This often means hand crafting your own find expression such that it's smarter than the default find expression that Test Studio built during recording.
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