You can choose to Show layout indicator which will show the language iso name in the system tray. You can choose to show the indicator even if you have a single layout enabled and you can show the language flag instead of only the ISO code by checking Show flag.

If you select Application or Window switching policy, changing the keyboard layout will only affect the current application or window. Global will change the keyboard layout globally and Desktop will change it only for the current virtual desktop.

Main shortcuts is a shortcut for switching layouts which is handled by X.org. 3rd level shortcuts is a shortcut for switching to a third level of the active layout (if it has one) which is handled by X.org. It allows modifier-only shortcuts. Alternative shortcut is a shortcut for switching layouts which is handled by Plasma™. It does not support modifier-only shortcuts and also may not work in some situations (e.g. if popup is active or from screensaver).

If you check Configure layouts you will be able to add and remove keyboard layouts in order to switch between them when you need.

Clicking on Add will open a dialog where you will be able to choose the new keyboard layout you want to add as well as its variant, label and shortcut.

The list of layouts right to the Layout label in the Add Layout dialog can be narrowed down using Limit selection by language drop-down list. You can click on Preview button to preview chosen layout in a separate window.

You can order the layouts with the up and down buttons, the top one being the default one.

This option can be enabled only if you have more than two layouts.

Spare layouts allow to toggle between small number of layouts easily while keeping more layouts handy close by. For example you might use 3 languages: English, Ukrainian and German but first two are used often and third one just occasionally. In this case you can configure first two as main layouts (setting Main layout count: 2) and German one as spare one - when you toggle with keyboard and left mouse button the switch will happen between main layouts only but you can always choose 3rd layout with context menu.

When spare layout is chosen it replaces the last main layout (this is done for technical reasons, usually global shortcuts work based on the 1st active layout so it's more reliable to preserve the 1st layout when allowing to activate spare layouts).

As X.org only allows to have 4 layouts to switch “spare layouts” feature also allows to overcome this limitation: user can have up to 4 main layouts (managed by X.org) but 4 more spare layouts allowed (managed by layout switcher). Thus user can conveniently work with up to total of 8 layouts (although the 4 spare layouts limit can be raised in the future).