https://knowledge.autodesk.com/.../autocad/.../How-to-assign-keyboard-function-keys...
Sep 19, 2015 - Here's an example of assigning F4 key to ORTHO ( video): Run CUI. On the left pane, expand ACAD > Keyboard Shortcuts > Shortcut Keys. Click Toggle Ortho. On the right pane, go to Properties > Access > Key(s). Click ... Enter F4 to assign it.