Here’s how to snoop/explore the Marionette Trailer in Nancy Drew: Mystery of the Seven Keys.
You can snoop and explore the marionette theatre trailer the day after Elka fixes your computer and you talk to Ned and Adela on the phone.
The marionette trailer will be open, step inside and walk up to the workbench. Pick up and read the clip board, noticing that Loutkari made a large donation.
Use the chisel (tool) on the jammed toolbox and read the script. Next to the workbench on the shelf is another set of papers.
Text Ned and ask him about Rezidente, then step out of the trailer and talk to Radek about the play today and about puppet number 12.
If you are Amateur Sleuth, you will now be able to check off the task item “Further investigate the marionette theatre.”
See the video for visual guidance: