I would like to add, that I too am having problems with Elementor as well. Below is what I have sent to them, and their response is, that this needs to be addressed to Flex. I have switched off all but the Elementor plugins, and switched to the basic theme as tests.
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Summary: Adding search fields for FlexMLS search plugin does not work
Message: This issue is while trying to edit the FlexMLS IDX Search widget.
While trying to add search options. One thing I notice is the icons do not seem to load properly for the plug in editor (screen shot 1), but the real issue is when when trying to add one of the search field options. The elementor editor reloads and ends up back at the main display, if you will. (See screen shot 2). To make this happen, Select a property type from the dropdown list, and click on the “add Type” button. Using the guentburg editor does work as designed, but kills all the cool stuff for the theme and Elementor options.