Some items have a translatable name.
This means that when you have such an item, what is displayed is not directly its name, but a translation of its name.
These items are easily identified : they have a property $_isNameTranslatable = true;
Most of these items are internal lists, not updatable through the tool.
But two of them can be modified : "profile" and "access mode".
They are easily identified, because under the name field appears the translated name (display only).
This means you can add one new item, but then how do you set its name ?

Here is an example on how to add a new profile :
Add the new profile, and set its name to a significant value, without spaces or special characters, and idealy starting with "profile" (to be easily identified in the translation table). For instance, we will name it "profileNewValue".
Enter all the other values as desired and save.
After saving, you can see displayed value is "[profileNewValue]", meaning this value is not found in the translation table.
You must then add a new line in the lang.xls file. First download it from the "download" menu.
Open in in Excel, and allow macros.
Then, you must add a new line in lang.xls, with string="profileNewValue" (example) and default, en, fr and de columns with the caption you want to display.
Then, "save as" (to position the default directoriy in Excel, don't use direct "save") and click on "Generate". This will generate a lang.js file in the current directory and in the en, fr and de sub-directories.
Then you may copy these files to replace existing ones in the /tool/i18n/nls directory on your server.
Just display the profile again : the name is now translated.

NB: don't forget to save your lang.xls file and identify your changes (for instance using vers. column) because you will have to re-apply them after each new version deployment.