Thanks for reaching out on the Lucidchart community. You can do these sorts of tasks by using the UI shape libraries. To start, simply open the shape library manager, search "UI", and select the shape libraries that you would like to use in this project. One shape that could be a good fit for your use case is the "Tree Pane" shape from the "UI Menus" shape library.
This shape defaults to looking like this:
With this markup:
You can edit this shape or any of the other UI shapes by hovering your mouse over the shape on your canvas and selecting "Edit Markup".
This shape is not the exact one that you described, but I believe it could be modified to achieve the desired effect.
Hope this helps!