Maybe this is a good case for a custom setting at the users preferences?

In T131803#2179149, @Luke081515 wrote:

Maybe this is a good case for a custom setting at the users preferences?

That's what I'm thinking. User setting or site setting or both. Generally on a huge screen there's a lot of unused space so we should be using that, but if people don't want that there's no good reason they shouldn't be able to turn it off and thus focus more on the content.

I think if you add an user setting for "Show always dropdowns". it should only change the behavior at huge screens if it is unset. Noone is happy if large sidebars are displayed at mobile view.

Yeah, option to just disable the sidebars and use the screen-small layout (the with dropdowns) for all aside from actual mobile. There's precedent.

I would appreciate having a single-sidebar option.
I'm not sure if the skin developers will add that option, so here is temporary workaround to add to your wiki's Timeless.css.

@media (min-width: 1340px) {
  #mw-content-block {
    display: block;
  }
  #mw-content,
  #content-bottom-stuff {
  margin-left: 14em;
  }
  #mw-content-wrapper {
    float: right;
    margin-left: -14em;
    width: 100%;
  }
  #mw-related-navigation {
    width: 14em;
    padding: 0 1em 0 0;
  }
}

Seems like a good one for after T122924: Merge Extension:Theme into core.

So we add some 'Desktop layout options':

• Single column layout with dropdown navigation
• Navigation in left-sidebar only
• Navigation and page tools in left and right sidebars

Where if it doesn't fit each will still scale down to the narrower ones; what this allows is disabling scaling up, essentially. Moo.

Change 530202 had a related patch set uploaded (by Isarra; owner: Isarra):
[mediawiki/skins/Timeless@master] Add settings to use a particular layout even at higher resolutions (cap at single column or single-sidebar instead of the default three- column mode)

https://gerrit.wikimedia.org/r/530202

Change 530202 merged by jenkins-bot:
[mediawiki/skins/Timeless@master] Add settings to use a particular layout even at higher resolutions

https://gerrit.wikimedia.org/r/530202

A note in case it gets implemented again (which I would appreciate a lot!): since T246296 there’s a much more convenient way to show the preference only on Timeless. As far as I understand, instead of

	/**
	 * Add preference(s)
	 *
	 * @param User $user
	 * @param array &$preferences
	 */
	public static function onGetPreferences( User $user, array &$preferences ) {
		$context = RequestContext::getMain();
		$useskin = $context->getRequest()->getVal( 'useskin', false );
		$skin = $useskin ?: $user->getOption( 'skin' );

		$defaultLayout = $context->getConfig()->get( 'TimelessDefaultLayout' );

		if ( $skin == 'timeless' ) {
			$layouts = [
				'one-column',
				'two-column',
				'three-column'
			];
			$layoutOptions = [];
			foreach ( $layouts as $layoutOption ) {
				$layoutOptions[$context->msg( "timeless-pref-$layoutOption" )->escaped()] = $layoutOption;
			}

			$preferences['timeless-layout'] = [
				'type' => 'select',
				'options' => $layoutOptions,
				'default' => $user->getOption( 'timeless-layout', $defaultLayout ),
				'label-message' => 'timeless-layout-preference',
				'section' => 'rendering/skin'
			];
		}
	}

it can be written as

	/**
	 * Add preference(s)
	 *
	 * @param User $user
	 * @param array &$preferences
	 */
	public static function onGetPreferences( User $user, array &$preferences ) {
		$context = RequestContext::getMain();
		$defaultLayout = $context->getConfig()->get( 'TimelessDefaultLayout' );

		$layouts = [
			'one-column',
			'two-column',
			'three-column'
		];
		$layoutOptions = [];
		foreach ( $layouts as $layoutOption ) {
			$layoutOptions[$context->msg( "timeless-pref-$layoutOption" )->escaped()] = $layoutOption;
		}

		$preferences['timeless-layout'] = [
			'type' => 'select',
			'options' => $layoutOptions,
			'default' => $user->getOption( 'timeless-layout', $defaultLayout ),
			'label-message' => 'timeless-layout-preference',
			'section' => 'rendering/skin/skin-prefs',
			'hide-if' => [ '!==', 'wpskin', 'timeless' ],
		];
	}

and it will automatically appear as soon as Timeless is ticked (not only after saving the skin preference) and disappear as soon as another skin is selected. (Please note that I haven’t tested this code, so it may contain typos or may not work in this form, but at least you get the idea.)