Absolutely! All the model files and blocks you create during your 30-day Trial period will seamlessly open in the comparable Model Developer Edition once activated...whether it's an Individual, Floating, or Node-Locked ExtendSim license. (Just be aware that if you build a model in a more feature-filled package like ExtendSim Pro, your model will not open properly in DE or CP if you have used blocks from the Reliability or Rate module in that model.)
And, once you activate your license, you'll notice the Trial version watermark on the model worksheet will disappear.
Please note, if you build a model in a Trial version and share it with someone who has a Student version of ExtendSim, they will not be able to open your model. Student versions can only open models built in an activated MDE license or from another Student version.