After publishing my first Mod, the current Mod integration within GC4 feels very weak. 
I do have some experience publishing around a dozen Mods for other games.
There seems to be a lack of versioning control for published Mods. At least from the website. Are you expecting users to manually delete their existing Mod and then resubmit a new one when they want to update / publish a bug fix?
If so, that is extremely primitive. (sorry guys, but it is...) 
Also, having to enter the Mod description at the point of the upload is also very wonky too.
I was sincerely expecting / looking for details on a Mod configuration file that would be placed in the root directory of the Mod. It would contain typical things like:
- Mod Name
- Author's Name
- Mod Description
- Mod Version
- Date
Much of the information I put in the associated markdown file, I expected would go into a required Mod configuration file.
Better Leader Traits.md
Also, when viewing what is on the Steam workshop, it appears you only have support for either Ship Mods or Race Mods, and nothing else. Really? There are other aspects of the game that you have provided Mod support for, but there is a lack of typical management of those kind of Mods via the Workshop.
As far as what is on your web site ( https://www.galciv4.com/mods/manager ), there is no mechanism to upload screen shots or any kind of feedback forum for users of the Mod.
To date, I have yet to see the integrated "Workshop" button actually function. I suspect that all it does is open up a weblink to the Steam Workshop page, but this is entirely a guess at this time.
As far as authoring the Mod itself, I did not encounter much of an issue. 
It was only later on publishing the Mod was I really disappointed on the lack of integrated Mod management support that currently exists in GC4.
I hope this is something you are looking to improve.... soon....