Hi DeliaBester,
Unfortunately there is no way to use Alt + number pad codes with Lenovo Yoga laptops, as there is no number pad emulation functionality on the keyboard. Manufacturers in general seems to be increasingly removing number pads behind, which is arguably a controversial change.
The built in function for many modern Lenovo laptops is using the On-Screen keyboard but I imagine that would be most inconvenient for your requirements.
Anyway, Charmap.exe is a good alternative, as well as AutoHotkey tool -- whilst AutoHotkey uses macros or quick combinations to get the characters you need. Another alternative is to use the Symbol functionality of your software applications - Microsoft Office applications from 2010 onwards allow you to customise the ribbon, so you can add Symbol to the Home tab.
External (bluetooth/wired) number pads might be your best solution.
Best,