Do you really have strings that look like dates instead of dates? I guess not.
I had to dow two tweaks to the FINDW function: stripping the blanks off _module, and using a blank as alternate delimiter:
data have;
infile datalines dlm="," truncover;
input usubjid :$20. visit :$20. date :yymmdd10. module :$20.;
format date yymmdd10.;
datalines;
101,SCREENING,2000-01-02,EG1
101,SCREENING,2000-01-02
101,UNSCHEDULED,2000-01-02,VS
101,UNSCHEDULED,2000-01-02,VS
101,UNSCHEDULED,2000-01-02,LB
101,UNSCHEDULED,2000-01-04,EG
102,SCREENING,2000-01-05
102,VISIT 1,2000-01-06
102,UNSCHEDULED,2000-01-06,VS
102,UNSCHEDULED,2000-01-07,LB
103,VISIT 1,2000-10-06,VS
103,VISIT 1,2000-10-06,VS
;
proc sort data=have;
by usubjid visit date;
run;
data want;
set have (rename=(module=_module));
by usubjid visit date;
length module $10; * set as needed for maximum number of modules;
retain module;
if first.date then module = "";
if findw(module,strip(_module),", ") = 0 then module = catx(",",module,_module);
if last.date;
drop _module;
run;
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