This discussion illustrates some of the issue mentioned in the ticket: user not being aware that the article can be published under the user namespace by changing the title, and uncertainty on how to edit it to achieve that.

This discussion illustrates another scenario where the options described in this ticket could help the user to do post-publish actions before making the article available to everyone.

Being able to add edit hashtags is a related usecase also mentioned here. I added the example in the description.

Another related comment from the discussion page.

During the template translation research (T161188) a participant described the urgency of fixing pending aspects of the article quickly before it gets deleted. In addition to the option to publish as a draft, the possibility of flagging that the user is still working on the content, could be of help too, which I added in the description.

I created a mockup to illustrate my initial thinking about this. Check the updated ticket description.

Change 353527 had a related patch set uploaded (by Santhosh; owner: Santhosh):
[mediawiki/extensions/ContentTranslation@master] WIP: Add publishing destination options

https://gerrit.wikimedia.org/r/353527

First iteration:

Based on @Volker_E comments on T193255, I illustrated how the settings would work when presented as part of a flyout and a dialog:

Flyout	Dialog

The flyout has the advantage of being more in-context (does not feel like a separate place) and fluent (does snot require a confirmation step, just changing the settings).
The dialog version has the advantage of providing more focus (the document fades away), and has less space constraints (extra room is available for more detailed descriptions).

Given that dialogs are currently available as standard widgets, and these actions don't benefit much from being in-context or are expected to be changed frequently, I think we can go with the dialog version. I'll update the description to reflect this.

Thanks @Pginer-WMF for the updates and the visual comparison!
After looking at those, I'm actually not as sure about the dialog option any more. Especially as I think your point about not requiring confirmation step is in this context stronger than the possibly gained focus.
Before opening the discussion between those two (the menu option has technical constraints, as you mentioned, width issues, no clear handling of widgets within menus yet in the standard library, etc.) again: Why not taking the Notifications way and provide a popup, extended from @santhosh's first iteration. This would also provide you with a flexible wrapper for future extensions and is in some ways an already familiar UI concept as well in contrast to the extended menu.
What were the reasons for you to move away from this?

In T133862#4196135, @Volker_E wrote:

Why not taking the Notifications way and provide a popup, extended from @santhosh's first iteration. This would also provide you with a flexible wrapper for future extensions and is in some ways an already familiar UI concept as well in contrast to the extended menu.
What were the reasons for you to move away from this?

My intention with the original design (F17612966) was for it to be supported as a flyout/popup. Since the only part currently implemented was the destination selection, @Esanders (probably unaware of the future plans for it) proposed a menu to be used in T193255 instead, and submitted a patchset. I tried to clarify the next steps in T193255#4171262, but developers were already in the process of reviewing the patchset and it got merged since technically it seemed correct.

The decision of which widget to use for the implementation may require to undo some of that work. I'd have preferred those discussions to happen before effort was put on coding to save time to everyone, but in the current situation I think it is better to focus the discussion on how is better to support the proposed functionality, and once that is decided to update the code accordingly.

One of the reasons I reconsidered the use of a dialog was that in terms of standardisation the building blocks are more clear. There are examples of dialogs in OOUI demo page and existing products, while the popups I've seen from the OOUI demo are very basic (showing just text), and creating a more complex UI requires to define many other aspects that may or may not become part of the recommendations when those are standardised.