[imexhouse]

Right below 'Note: To enter the values of language variables in the correct charset please select the desired language from the dropdown box at the top of this page.', there are two drop down lists:
'Select topic' and 'Apply filter'
In the 'Select topic', select 'Text', and in the 'Apply filter' type: txt_welcome

It will show you in a window below the 'txt_welcome' text that you can then edit.