TYPO3 Core

The quick workaround might be to set min-width= XX and width=100% in styles of element with class: typo3-dyntabmenu-divs
This of course won't change much if we resize browser to small sizes where the wole content ara is very small but for "normal" usage it will be much better,

Felix, can you please take a look at this?

From what i see it can be changed/fixed without any modifications in current CSS. The fixed styles are hardcoded in:

typo3/sysext/backend/Classes/Controller/ContentElement/NewContentElementController.php

we have there:

if ($this->config['renderMode'] == 'tabs') {
$this->doc->inDocStylesArray[] = '
.typo3-dyntabmenu-divs { background-color: #fafafa; border: 1px solid #adadad; width: 680px; }
.typo3-dyntabmenu-divs table { margin: 15px; }
.typo3-dyntabmenu-divs table td { padding: 3px; }
';
$code = $GLOBALS['LANG']->getLL('sel1', 1) . '<br /><br />' . $this->doc->getDynTabMenu($menuItems, 'new-content-element-wizard', FALSE, FALSE);
} else { ...

We can remove all $this->doc->inDocStylesArray[] part because we dont want fixed size and if renderMode is set to tabs there are no tables in tab body but lists so we dont need any styles for tables.

I'll send proposed patch for this.

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/26906