How can I import a list of words and shortcuts into my Android Personal Dictionary?
I had a look at your file and couldn't import the words to Gboard either. There are 3 errors that make Gboard ignore your words and shortcuts: space between words &amp; shortcuts and no language for the words.

Error 1:  Space between words & shortcuts

Your words and shortcuts are separated by spaces. That's not correct. They must be separated by Tab. I didn't know that either. I created some words and shortcuts, then exported them. When I opened the exported file in a code editor, only then could I see that the separator was not a space but a tab character.

Error 2:  No language for the words

This error is minor. Your words didn't belong to any dictionary language. It seems when you don't add the language, the words &amp; shortcuts are not imported or GBoard just decides to ignore and select a language for you (I have not checked why). So, you must add a language at the end of each words separated of course by Tab characters. 

Error 3:  No dictionary version

Add the dictionary version at start of the file. GBoard ignores the language (see Error 2) which is bad if like me you have many languages enabled.

I have not found yet how to add words to the "All languages" dictionary (although you didn't ask).