I have had little luck in finding an answer to this simple question in the blender manual, stack exchange, and reddit answers. While you can easily set a new custom transform orientation manually by clicking on the button seen below, this can add up to be quite cumbersome while modelling for extended periods of time. (the shortcut ctrl + alt + spacebar brings the workspace into full screen, it does not act as a shortcut for transform orientation). Thanks for your help!
I don't see a reason people hesitate to answer this question. It is exactly as it seems:
There is no keyboard shortcut for creating custom transform orientation in the default keymap in Blender 2.93.
You can find this out by searching "Create Orientation" in the Preferences, Keymap tab. If you find nothing, it means there is no hotkey.
You can right-click on the button and assign a custom hotkey or add the function to quick favourites menu if you need to use it often.
You can easily create a keyboard short-cut for almost any button in Blender. Simply right(or left click) the plus option in Transform Orientation in the 3D view. Scroll down to Assign Shortcut, and enter any prompt you'd like.
Recommendation: Since the keyboard shortcut for changing Transform Orientation is ' , ' (comma). I suggest you make this new one Ctrl+ ,