Going to be difficult to get help on this unless someone else in the Wappler forum is already using Directus to do something similar. Wappler is a low code solution and can be as simple or as powerful as needed depending upon multiple factors, one of them being the API provider you are using and the complexity of your workflow, yours being a pretty unique situation in this case where you are not directly editing your database and need to go through a third party.
To assist I would need to create a dummy database, connect it to a Directus account and then read through their API documentation to even begin trying to assist.
My totally honest opinion however is that it makes no sense to have to make your database adjustments via Directus, it’s kind of like 3 friends chatting and you whisper something to Fred and then Fred has to tell Bob every word you say verbatim.
Seems like an unnecessary complication, and it is going to make your build way more complicated from your side.
Even getting help is going to be more difficult as you can already see as the userbase of MySQL people around is massive however the userbase of Directus controlling a database I am sure would be far smaller.
Maybe you could explain that to your web developer so he can give you direct access to the database, or limited database user access for security, only to the tables you need to adjust and reduced privileges.
By reading the Directus site they seem to completely replicate your database data, therefore any database change you make should sync through to Directus platform.
I do however understand that sometimes these things are entirely out of our control and maybe in your situation you are forced to have to go this odd way around making your database alterations, in which case maybe someone else has some experience working with this particular service.
@wappler_ambassadors has anyone got any experience using Directus that can try give a little guidance.
As a last resort you could private message me authentication details and i could take a look in your real world scenario and try assist, thats your call though.