This is what the manual of Chessbase says about this option:
So the function "collect opening" creates merged games for each seperate opening find in the datase.The program generates a new database that contains all the games that start with the same moves (openings variant) gathered together. This gives you a good overview of the openings in the database, just like the openings encyclopedia.
I use this function to further devide my repertoires in small chunks.
Without having to use a seperate game for each seperate variation.
For my Queen's Gambit repertoire for white it gives me 23 seperate sub-repertoires for example.
That make it easyer to study the opening and to memorize the lines, in Chessable for example:
The problem is that the collect openings feature doesn't work perfect in Chessbase.D07 [Queen's Gambit: Chigorin]
D11 [Slav Defence: 3 Nf3 sidelines]
D15 [Slav Defence: 4 Nc3 a6 and 4 Nc3 Bf5]
D16 [Slav Defence: 5 a4: Lines with 5...Bg4 and 5...e6]
D17 [Slav Defence: 5 a4 Bf5: Lines with 6 Ne5]
D20 [Queen's Gambit Accepted: 4 e4]
D21 [Queen's Gambit Accepted: 3 Nf3 sidelines]
D22 [Queen's Gambit Accepted: 3 Nf3 a6 4 e3]
D25 [Queen's Gambit Accepted: 4 e3 : sidelines and 4...Bg4]
D26 [Queen's Gambit Accepted: 4 e3 and 5 Bxc4 c5 sidelines]
D27 [Queen's Gambit Accepted: Classical main line: 7.Bd3]
D30 [Queen's Gambit Declined: Systems without Nc3]
D31 [Queen's Gambit Declined: Semi-Slav without ...Nf6]
D32 [Tarrasch Defence: Sidelines and lines without g3]
D35 [Queen's Gambit Declined: Exchange Variation]
D36 [Queen's Gambit Declined: Exchange Variation: Main line]
D37 [Queen's Gambit Declined: 5 Bf4]
D38 [Queen's Gambit Declined: Ragozin Defence 4 Nc3 Bb4]
D39 [Queen's Gambit Declined: Ragozin Defence with 6 Bg5]
D41 [Queen's Gambit Declined: Semi-Tarrasch]
D43 [Semi-Slav: 5 Bg5 h6]
D44 [Semi-Slav: Botvinnik System and 5...Nbd7]
D46 [Semi-Slav: 5 Nf3 Nbd7 6 Qc2 Black avoids the Meran]
Some lines are missing and are not to be find in the output database.
So I hope Hiarcs Explorer Pro could include a similar option to collect openings from a database without the error of some opening lines missing.