I think Spacebar should work to End Turn just as well as Enter. It's much more convenient to avoid moving the mouse hand or cursor. You can use two keys CTRL+Spacebar to do the same thing but it is less convenient than just hitting one key. So this guide tells you how to make Spacebar do both. Alternatively you can just assign it to Left Shift if you prefer (see below.)

I have devised an AutoHotKey script to do just this thing:

You must have a 1.x version of AutoHotKey installed to launch or compile this. It is free, open-source software.
You can get a copy of that here:
(Direct Link)
https://www.autohotkey.com/download/ahk-install.exe
Site: https://www.autohotkey.com/

Save the following to a file from a Notepad instance:

SpaceisalsoEnter.ahk

Make sure you save it with .ahk extension or rename it afterwards from whatever.txt to whatever.ahk

Now your script is ready. When you have AutoHotKey installed you can run it and it will pop up an icon in the taskbar. This lets you enable or disable it or just close out the script so it will stop working until you launch it again. When running this script works to make your Spacebar count for two: It works as Space and then it will work as Enter a half-second later.

Optional:
You can also make a variation on it by changing the code like this if you want Left Shift to work as enter, versus Spacebar working as both. Just replace the second section with this:
LShiftisenter.ahk

For while the script is running your left Shift button will act only as Enter.

If you wish to use both, this is the single AHK file to create Alltheenters.ahk:

Note: To access Steam Overlay while this is active, use Right Shift and Tab. Or include the Suspend line at the end of the last code block to create a toggle without clicking.

You're welcome. If you find this helpful awards are appreciated.