Bulk word import into Gboard I moved from my Redmi to Mi Mix 2 now and used the Mi Mover app but unfortunately, the words in my used keyboard Gboard weren't restored. Neither does the internal synchronization work, it says something like &quot;sync is not available for devices with G suite accounts or Android for work profile&quot;.
Couldn't yet find a working solution for this issue, so I'm thinking about re-adding all words but don't want to do this one by one. I have a wordlist as a text file that would cover at least 80% of my custom words. Any way of adding this at once to Gboard dictionary?
Apart from Gboard dictionary, there seems to be a common Central Android custom word dictionary. Is Gboard also considering words from there? In case it is, maybe there's some API/interface to this Central place so I could add those words at least there, so they could be used by Gboard (and also by other keyboard apps should I ever decide to switch).
I don't mind which way to go in case at least one of both could be achieved.
I have just managed to move my Swype dictionary to Gboard and would like to share my technique. Please bear in mind that I am not able to program, so this technique is aimed at novices like myself. I used Android 9 on a Samsung Note 8.
I know it looks like a long and complicated process, but that's just because I've broken it down into small steps: if you have less than a thousand personal words in your vocabulary the whole thing shouldn't take more than about half an hour. At the end of the process, I uninstalled the two apps which I had installed, but that of course is up to you.

Open Swype and go to Edit My Dictionary.
Install and open Universal Copy: I found it on the notification bar
Tap the top-right icon which is a dotted square surrounding a solid rectangle. This will select everything on the screen. Then press the Copy icon which is two overlapping rectangles
Because I have Word on Android, I opened a new Word document and pasted into it the words that Universal Copy had copied. (It would probably have been quicker to use ES File Explorer to create a plain-text .txt file, but I did not think of this until too late).
Press Enter after the last word pasted so the cursor will be on a new line
Go back to Edit My Dictionary and scroll up until the words you have already copied have disappeared at the top of the screen
Go back to Universal Copy, which means going back to the notification bar at the top of the screen, and repeat steps 3 to 6 however many times you need to copy all the words from your Swype dictionary. (I have more than 700)
Optionally, go through the Word or .txt document you have just created, cutting out all the repetitions of &quot;Personal Dictionary&quot; which Universal Copy has faithfully copied each time it saw it on the screen. Also, remove any unwanted words on that list.
If you created a .txt document, call it wordlist.txt. If you created a Word document, you will need to Save As wordlist.txt. I had to do this and the next step on the PC but  I'm sure it's possible to do it on the phone.
Whichever way you created this wordlist.txt file, move it to the root of the SD card
Install and open User Dictionary Manager to import this file into your Android Personal Dictionary.
The most difficult part for me was finding the path to the root of my SD card. In the end, I found it on a Google app called Files, by selecting the file and then tapping the Information icon on the drop-down menu. My path was /storage/14B5–E887/wordlist.txt. Obviously your SD card will not be called 14B5–E887, and depending on your version of Android and your phone, you may have a different path altogether.
The most satisfying part was checking this had worked by going TG board, choosing Settings, Dictionary Personal Dictionary, English (UK) and seeing all your Swype words appear… For some reason in duplicate :-( but this does not seem to matter.