>>The above code doesn't work anymore :(

Assign the image source to a lcImageSource variable and wrap it in () in the copy memo. If it might be an expression, check for a bracket and eval() it first. This lets you do away with the macro substitution as well...

CREATE CURSOR test (myval m)
APPEND BLANK

Savefile("myval",ADDBS(SYS(2023))+"t1.txt")
Savefile("GetMyval()",ADDBS(SYS(2023))+"t2.txt")

FUNCTION SaveFile(lcimagesource,lcFilename)
REPLACE myval WITH m.lcImagesource
IF "(" $ m.lcimagesource
	lcimagesource=EVALUATE(m.lcimagesource)
ENDIF
COPY MEMO (m.lcImageSource) to (m.lcFilename)
MODI FILE (m.lcFilename)
ERASE (m.lcfilename)
RETURN

FUNCTION GetMyval()
RETURN "myval"