Trees

Edit in the lower panel to get what you wish, using the palette or copies of
     ~   &   ∨   →   ≡   ∃  ∀  ◊  □  ∴
For example, F, F→G ∴ G (it is common to list a number of premises, separated by commas, followed by a therefore sign, and then a conclusion).
Then select what you are interested in (don't select extra junk) and click Start from selection.
You can drag and drop into the panel from Web pages, other documents, etc. .