How to add content (text) to an ASCII based file

[Gintaras]

-opening as text with Notepad
-find the text via 'windowtext.find'
-keyboard to the end of the line
-paste from the clipboard

Get file data with str.getfile. It stores file text in the str variable.
Find the text with one of QM 'find string' functions.
Insert text. Or find-replace in one step.
Save with str.setfile.