How do I copy and paste properties (such as "set variables") of one interaction inside another interaction?

Hi Karinna,
Thanks for reaching out to the community! This is in our radar.
Here is our official statement, that you can also find in our Help Center article: here

To give more clarification, currently, if you copy and paste objects to different file, the prototype will continue to work as the variables transfer over. However, any unpublished variables applied to prototypes won’t be available for further use, like when creating Set variable actions, or switching an object’s number variable.

We are working on improving transferring variables across files. As a workaround, either recreate the variables in the destination file, or duplicate the original file.

If the original file is published to team libraries, copied and pasted variables will work as expected.

If you receive a notification that pasting unpublished variables across files won’t create new local variables yet, try publishing the source library and and enabling it in the destination file.

Others in the community have also requested this feature request, feel free to vote up and share your feedback here: Copy and paste a portion or all of an interaction

Hope it helps!