I like foobar because you can import the tags from various places online, so it doesn't have to be done by hand. Hopefully the other suggestion will do the same thing.
In the situation I describe I think that Foobar should allow to change the tags manually to make the GUI order correctly.
I have the following tracks names and the GUI orders them based on the i ii iii iv... caracters:
01-01-Act_I_i_Vorspiel_und_Erste_Szene-LLS.flac
01-02-Act_I_ii_Wes_Herd_diess_auch_sei-LLS.flac
01-03-Act_I_iii_Einen_Unseligen_labtest_du-LLS.flac
01-04-Act_I_iv_Zweite_Szene_Mud_am_Herd-LLS.flac
01-05-Act_I_v_Friedmund_darf_ich_nict_heissen-LLS.flac
01-06-Act_I_vi_Die_so_leidig_Los_dir_beschied-LLS.flac
01-07-Act_I_vii_Ich_weiss_ein_wildes_Geschlech-LLS.flac
01-08-Act_I_viii_Dritte_Szene_Ein_Schwert_verh-LLS.flac
01-09-Act_I_ix_Schlafst_du_Gast-LLS.flac
01-10-Act_I_x_Wintersturme_wichen_dem_Wonnemon-LLS.flac
01-11-Act_I_xi_Du_bist_der_Lenz-LLS.flac
01-12-Act_I_xii_O_susseste_Wonne-LLS.flac
01-13-Act_I_xiii_Siegmund_heiss_ich-LLS.flac
02-01-Act_II_i_Vorspiel_und_Erste_Szene-Nun_za-LLS.flac
02-02-Act_II_ii_Hojotoho-LLS.flac
02-03-Act_II_iii_Der_alte_Sturm_die_alte_Muh-LLS.flac
02-04-Act_II_iv_Heut-hast_du_s_erlebt-LLS.flac
02-05-Act_II_v_Nichts_lerntest_du-LLS.flac
02-06-Act_II_vi_Was_verlangst_du-LLS.flac
02-07-Act_II_vii_Deiner_ew_gen_Gattin_heilige_-LLS.flac
02-08-Act_II_viii_Zweite_Szene_Schlimm_furcht_-LLS.flac
02-09-Act_II_ix_Ein_Andres_ist_s_achte_es_wohl-LLS.flac
02-10-Act_II_x_So_nimmst_du_von_Siegmund_den_S-LLS.flac
02-11-Act_II_xi_So_nimm_meinen_Segen_Niblungen-LLS.flac
03-01-Act_II_xii_Schwer_wiegt_mir_der_Waffen_W-LLS.flac
03-02-Act_II_xiii_Dritte_Szene_Raste_nun_hier_-LLS.flac
03-03-Act_II_xiv_Wo_bist_du_Siegmund-LLS.flac
03-03-Act_II_xiv_Wo_bist_du_Siegmund-LLS.flac
03-04-Act_II_xv_Vierte_Szene_Siegmund_Sieh_auf-LLS.flac
03-05-Act_II_xvi_Du_sahst_der_Walkure_sehrende-LLS.flac
03-06-Act_II_xvii_So_jung_un_schon_erschimmers-LLS.flac
03-07-Act_II_xviii_Funfte_Szene_Zauberfest_bez-LLS.flac
03-08-Act_II_xix_Der_dort_mich_ruft-LLS.flac
03-09-Act_II_xx_Zu_Ross_dass_ich_dich_rette-LLS.flac
04-01-Act_III_i_Vorspiel_und_Erste_Szene_Hojot-LLS.flac
04-02-Act_III_ii_Zu_Ortlinde_s_Stute_stell_dei-LLS.flac
04-03-Act_III_iii_Schutzt_mich_und_helft_in_ho-LLS.flac
04-04-Act_III_iv_Nicht_sehre_dich_Sorge_um_mic-LLS.flac
04-05-Act_III_v_Zweite_Szene_Wo_ist_Brunnhild-LLS.flac
04-06-Act_III_vi_Hier_bin_ich_Vater-LLS.flac
04-07-Act_III_vii_Dritte_Szene_War_es_so_schma-LLS.flac
04-08-Act_III_viii_So_tatest_du_was_so_gern_zu-LLS.flac
04-09-Act_III_ix_Nicht_streb_o_Maid-LLS.flac
04-10-Act_III_x_Leb_wohl_du_kuhnes_herrliches_-LLS.flac
04-11-Act_III_xi_Der_Augen_leuchtendes_Paar-LLS.flac
04-12-Act_III_xii_Loge_hor_Lausche_hieher-LLS.flac