Improve visuality of 'Mark as done' button to avoid confusion with 'Save'

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Is your feature request related to a problem? Please describe.
I'm setting up Nextcloud for a lot of people that aren't that technically confident. Also, they come from a environment where most things they make, a document, and e-mail, etc, require hitting a 'Save' button to actually save the item.

When the create a deck, many will hit the 'Mark as done' button expecting the card to be saved and closed. I must say, I fell for this one myself the first few times.

Luckily, the button changes so you can revert the marking.

Describe the solution you'd like
I've a few possible ideas:

• hide the "mark as done" button while creating a new card
• move the button entirely, the 'Mark as done' action is already available in the dot menu next to the x to close the card.
• keep the button, but style it differently
• make it clearer the card is already saved
• add a 'confirm card' button

Describe alternatives you've considered
Add custom CSS to hide the card.

.modal__card .completed-button {
    display: none !important;
}

Additional context
Running:

• Deck Version 1.17.4
• Nextcloud AIO v13.4.1 / Hub 26 Winter (33.0.7)

The issue names the frontend selector .modal__card .completed-button but no source file or test. Start by locating that selector and inspecting the card-creation modal and its Mark as done control. The issue is done when users can distinguish saving a new card from marking it complete; the specific visual or placement change still needs agreement.