If you want to use same “SAPGui Logon Language” selection for all your SAP systems then you can check the following configuration.

Open your SAPGUI “Options” page like shown below

Select the  “SAP Logon Options” title and click the “General” area to open related screen on the right side

Check the  “Use SAP Logon language as default on logon screen” option to use chosen language as DEFAULT for all SAP systems which are configured in you SAP LOGON tool

For example select the language “DE”

Try to logon a SAP system and control the “language” area ;

Now for the another example , select the EN for the default language

Let’s try to logon same SAP system ;

As you can see , if you click the “Use SAP Logon language as default on logon screen” selection and choose a logon language then you can use this language for all you SAP system logon screens.