You are working with the ALV "Classic" function module REUSE_ALV_LIST_DISPLAY. 

Reading the documentation for the function module, it seems there is a way to save an ALV layout variant as "user-specific" and/or "global". But unfortunately, you either can only save "globals" (with the '/' as first character of the layout name) or "user-specific". 

You have tried the I_SAVE parameter as 'U' and can only save "user-specific". You tried I_SAVE as 'X' and can only save "global". You tried I_SAVE as 'A', but only can only save as "user-specific". The odd thing is, on the Save Layout pop-up dialog the User-Specific checkbox is always "greyed-out", but has a check (for 'U' and 'A') or is checkless (for 'X').

Can "user" and "global" layout variants be saved together from same program with I_SAVE as 'A'? 

Why is the User-Specific checkbox on the Save Layout pop-up always "greyed-out"?

You have the following EXPORTING parameters in my function module:
I_DEFAULT = 'X'
I_SAVE = 'A' "<=== this is to be global & user IS_VARIANT = VARIANT

VARIANT has the program's name in the REPORT field.

The "user-specific saving" needs a special authorization:
Authority-check object 'S_ALV_LAYO' id 'ACTVT' field '23', you can
avoid this authorization with IS_LAYOUT-NO_AUTHOR = 'X'.

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