If you need to work a lot with the Pathfinder panel, you are interested in the acceleration your actions, aren't you? The decision is the setting of shortcuts for the most frequent operations. Open the Illustrator, create there the new document and let's see how to do this...
Take, for example, the Ellipse Tool (L) and create two overlapping elliptical paths.
When the paths selected, the Pathfinder panel can allow you to manipulate them in the geometrical sense. For instance, the Unite button converts two ellipses in only one path.
In order to do this function using the shortcuts, first, go to Window > Actions.
Then select both our ellipses (or your own paths) and click the Create New Action button. Follow the image below for reference.
Name the action as you like in the opened dialog box, and choose any functional key for it in the list. The chosen key will be a shortcut for the union of the paths. Pay attention that if another operation is assigned with this key, it will be reset to the new one. So, use such a key that, you are sure, free in your work.
After the function key is chosen, you may create a key combination from it by setting the Cmd/Ctrl and Shift options in the dialog box. Follow your own desire. I prefer use only function key and leave the additional options blank. Click the Record button in the dialogue box. So, as you see it, I have used the F7 key.
Then go to the Pathfinder panel and click the Unite button.
Then immediately click the Stop Playing / Recording button in the Actions panel.
Now you may close the Actions and the Pathfinder panel. Create any new two overlapping paths so as to control the work of your shortcut. Select them.
Press your shortcut. F7 in my own work.
Thus you may assign any shortcuts for all the buttons in the Pathfinder panel and forget about it forever. What is the Pathfinder panel? I do not remember...