Oh I see what you mean:
FUNCTION define_collapsible_group_style()
DEFINE attdefs DICTIONARY OF STRING
LET attdefs["collapsible"] = "yes"
LET attdefs["backgroundColor"] = "lightBlue"
CALL style_define("Group.collapsible", attdefs)
END FUNCTION
Yes, this is direct AUI tree manipulation, to create a new style for groups, from the program instead of adding a .4st file to the tool.
Since .4st style files have no inheritance, if you want to use the latest changes in FGLDIR/lib/default.4st, this is the best solution I found.
Regarding style usage in DISPLAY ARRAY to decorate individual cells with setArrayAttributes(), we have the request
https://4js.com/support/issue/?id=FGL-01470#startissue, to use styles instead of simple colors, but that is rejected, and anyway would not help you since you don't like setArrayAttributes().
I do not see how DISPLAY ARRAY ... ATTRIBUTES(STYLE=...) would help to decorate individual cells.
Are you asking for a way to defined a global style that would apply to all data rows in the TABLE?
This is possible by specifying a STYLE in the TABLE definition in the .per.
I am not sure to understand your request.
Seb