Hi there, while display logic cannot be added to txt imports, you should be able to copy an existing survey that contains the questions/display logic from your Survey Library into your main survey.
First, create a survey and configure it with the questions and display logic you would like to copy into your main survey. To add this configured survey to your Survey Library, follow the steps here or do so from the Projects page using Project Actions.
Once the configured survey is saved to the Survey Library, head back over to the main survey and select "Import from Library" at the bottom of a survey block. Navigate to the where the configured survey is saved and then select "Insert Entire Survey".
This looks to only be necessary for display logic that is based on survey questions. If the display logic is based on Embedded Data or Device Type, you should be able to copy just the question from an existing survey by selecting "Import from Library", then "Copy from an Existing Survey" and navigating to the configured survey question.