In Versions prior to 12.2 quite complicated objects (with java dependency) were required.
Fortunately, in 12.2 Oracle introduced (& documented) the View V$DIAG_TRACE_FILE_CONTENTS. Unfortunately for some (only good from an internal technical perspective) reasons it does not contain the file itself, or a LOB locator, but several chunks as VARCHAR2. So it's still worth to write some code for a simple interface to access the tracefiles.
Again it's a SQLDeveloper report. But the structure is so simple, it can be implemented in any preferred tool.
There is a simple list of tracefiles and their MODIFY_TIME as FILEDATE - based on V$DIAG_TRACE_FILE.
When a specific tracefile name is selected, the file is presented as text and BLOB. The content is identical, just BLOBs can be downloaded which is useful for huge tracefiles, whereas the CLOB representation is simple to directly read small tracefiles. Fortunately no objects are required in the database, only proper grants on V$DIAG_TRACE_FILE and V$DIAG_TRACE_FILE_CONTENTS. These can be roles also.
As I have limited access to databases right now, I could not test a lot of settings, e.g. RAC or different character sets.
Just import this Report as an User Defined Report:
<?xml version="1.0" encoding="UTF-8" ?>
<displays>
<display id="04e5e018-014a-1000-8001-ac193119805c" type="" style="Table" enable="true">
<name><![CDATA[get tracefiles]]></name>
<description><![CDATA[create a list of tracefiles as listed in V$DIAG_TRACE_FILE and makes specific files available]]></description>
<tooltip><![CDATA[create a list of tracefiles in DIAG directory and makes specific files available ]]></tooltip>
<drillclass><![CDATA[null]]></drillclass>
<CustomValues>
<TYPE>horizontal</TYPE>
</CustomValues>
<query>
<sql><![CDATA[select TRACE_FILENAME as TRACE_NAME ,
MODIFY_TIME as FILEDATE
from V$DIAG_TRACE_FILE
Order By MODIFY_TIME desc]]></sql>
</query>
<pdf version="VERSION_1_7" compression="CONTENT">
<docproperty title="-" author="berx" subject="-" keywords="-" />
<cell toppadding="2" bottompadding="2" leftpadding="2" rightpadding="2" horizontalalign="LEFT" verticalalign="TOP" wrap="true" />
<column>
<heading font="null" size="10" style="NORMAL" color="-16777216" rowshading="-1" labeling="FIRST_PAGE" />
<footing font="null" size="10" style="NORMAL" color="-16777216" rowshading="-1" labeling="NONE" />
<blob blob="EMBED" zip="false" />
</column>
<table font="Agency FB" size="10" style="NORMAL" color="-16777216" userowshading="false" oddrowshading="-1" evenrowshading="-1" showborders="true" spacingbefore="12" spacingafter="12" horizontalalign="LEFT" />
<header enable="false" generatedate="false">
<data>
null </data>
</header>
<footer enable="false" generatedate="false">
<data value="null" />
</footer>
<security enable="false" useopenpassword="false" openpassword="null" encryption="EXCLUDE_METADATA">
<permission enable="false" permissionpassword="null" allowcopying="true" allowprinting="true" allowupdating="false" allowaccessdevices="true" />
</security>
<pagesetup papersize="LETTER" orientation="1" measurement="in" margintop="1.0" marginbottom="1.0" marginleft="1.0" marginright="1.0" />
</pdf>
<display id="null" type="" style="Table" enable="true">
<name><![CDATA[get tracefile]]></name>
<description><![CDATA[access the specific tracefile ]]></description>
<tooltip><![CDATA[Specific tracefile from list above ]]></tooltip>
<drillclass><![CDATA[null]]></drillclass>
<CustomValues>
<TYPE>horizontal</TYPE>
</CustomValues>
<query>
<sql><![CDATA[with function get_tracefile (filename varchar2) return CLOB IS
-- PRAGMA AUTONOMOUS_TRANSACTION;
-- to avoid ORA-14553: cannot perform a lob write operation inside a query
-- only required in dedicated function
--
-- in a dedicated function, this grant is required:
-- grant select on sys.V_$DIAG_TRACE_FILE_CONTENTS to xxx;
l_out CLOB := EMPTY_CLOB;
CURSOR all_payload (fn varchar2)
is
Select Payload
from V$DIAG_TRACE_FILE_CONTENTS
where trace_filename=fn
and payload is not null
order by line_number asc;
begin
NULL;
DBMS_LOB.CREATETEMPORARY(l_out, FALSE, DBMS_LOB.CALL);
for r_payload in all_payload(filename)
loop
DBMS_lob.append(l_out, r_payload.payload);
end loop;
return l_out;
DBMS_LOB.FREETEMPORARY(l_out);
end get_tracefile;
function get_tracefile_blob (filename varchar2) return BLOB IS
-- PRAGMA AUTONOMOUS_TRANSACTION;
-- to avoid ORA-14553: cannot perform a lob write operation inside a query
-- only required in dedicated function
--
-- in a dedicated function, this grant is required:
-- grant select on sys.V_$DIAG_TRACE_FILE_CONTENTS to xxx;
l_out BLOB := EMPTY_BLOB;
CURSOR all_payload (fn varchar2)
is
Select Payload
from V$DIAG_TRACE_FILE_CONTENTS
where trace_filename=fn
and payload is not null
order by line_number asc;
begin
NULL;
DBMS_LOB.CREATETEMPORARY(l_out, FALSE, DBMS_LOB.CALL);
for r_payload in all_payload(filename)
loop
DBMS_lob.append(l_out, utl_raw.cast_to_raw(r_payload.payload));
end loop;
return l_out;
DBMS_LOB.FREETEMPORARY(l_out);
end get_tracefile_blob ;
select get_tracefile(:TRACE_NAME) as " Tracefile", get_tracefile_blob(:TRACE_NAME) as " Binary Tracefile " from dual]]></sql>
<binds>
<bind id="TRACE_NAME">
<prompt><![CDATA[TRACE_NAME]]></prompt>
<tooltip><![CDATA[TRACE_NAME]]></tooltip>
<value><![CDATA[NULL_VALUE]]></value>
<bracket><![CDATA[null]]></bracket>
</bind>
</binds>
</query>
<pdf version="VERSION_1_7" compression="CONTENT">
<docproperty title="-" author="-" subject="-" keywords="-" />
<cell toppadding="2" bottompadding="2" leftpadding="2" rightpadding="2" horizontalalign="LEFT" verticalalign="TOP" wrap="true" />
<column>
<heading font="null" size="10" style="NORMAL" color="-16777216" rowshading="-1" labeling="FIRST_PAGE" />
<footing font="null" size="10" style="NORMAL" color="-16777216" rowshading="-1" labeling="NONE" />
<blob blob="EMBED" zip="false" />
</column>
<table font="null" size="10" style="NORMAL" color="-16777216" userowshading="false" oddrowshading="-1" evenrowshading="-1" showborders="true" spacingbefore="12" spacingafter="12" horizontalalign="LEFT" />
<header enable="false" generatedate="false">
<data>
null </data>
</header>
<footer enable="false" generatedate="false">
<data value="null" />
</footer>
<security enable="false" useopenpassword="false" openpassword="null" encryption="EXCLUDE_METADATA">
<permission enable="false" permissionpassword="null" allowcopying="true" allowprinting="true" allowupdating="false" allowaccessdevices="false" />
</security>
<pagesetup papersize="LETTER" orientation="1" measurement="in" margintop="1.0" marginbottom="1.0" marginleft="1.0" marginright="1.0" />
</pdf>
</display>
</display>
</displays>
Any comments, hints or recommendations are highly welcome!
Beside the functionality to trace a current statement/script, in Version 2.0.0.43 of Method R Trace There was another functionality (called feature 2) to list all tracefiles 
