If you expect to be able to do many things on a selection with the Lasso tool, but instead only see the "Take Screenshot" command, the Lasso tool is likely misconfigured to select only certain objects.
To check, tap the Lasso tool twice and make sure to enable all the relevant options. For example, if you're looking to manipulate handwriting, make sure "Handwriting" is enabled under the Lasso tool options. Then try drawing a loop around the object and see if you can manipulate it.
If you still can't see any other command, it's likely you're trying to select the text of a PDF page. Please note that the Lasso only selects annotations created with GoodNotes. As a workaround, you can take a screenshot of the PDF text and the screenshot can be copied and pasted to the page.