I want to build an opening repertoire manually. what are the computer tools to do that?
It depends on what you mean with "best".
The objectively best tool, and the tool that nearly all professionals use, is ChessBase with the Mega Database (highest-quality and most comprehensive chess database that exists) and a strong engine (often, they use cloud engines, e.g. from Chessify, so that they can reach high depth get impressions from what different engines think (e.g. SF vs LC0). It has many advanced functions that assist you in creating, for example automated novelty mining. ChessBase is not only one of the best, but also one of the most expensive tools out there, asking for hundreds of dollars if you want the complete package.
I think that you are not so much interested in the "best", but in the "most suitable" tool for your needs. If you are not a master-level player (which I assume, otherwise you'd not ask and know ChessBase and other tools already), then the free lichess opening explorer (click on the book icon) is most likely the most suitable tool for your needs, especially if you are intending to create an online-chess repertoire. Unlike ChessBase, it doesn't provide any automated tools and functions to create a repertoire or mine novelties, but a database and a strong engine should be sufficient to create a repertoire manually.
You can organize and save your repertoire in a lichess study (which is somewhat an online PGN file), where you can have multiple chapters, one for each line you want to analyze. The only drawback is the chapter limit, but when a lichess study is full, you can just create another one. The lichess DB is frequently checked and referenced in newer Chessable courses, so it's actively used by authors to check how well their lines work in practise online.
Chess.com also has similar features as lichess for creating a repertoire, but I don't see why one would need to pay for it when lichess provides the same service for free.
SCID + free DB (e.g. CaissaBase)
If both good options from above are not suitable for you (because you need offline and free solutions), the best is probably to use a free Chess Database software (e.g. SCID or SCID vs PC), add StockFish16 as an engine and look for a free PGN base that you can download online to estimate the success rates of the moves. Note however, that there exist no completely satisfactory free chess databases (and that very large databases such as a download of the lichess database are pretty much infeasible, especially for free software). One of the best that is available for free is certainly the CaissaBase.
SCID allows you to create chess databases (that you can later export as PGN, if you need them anywhere else) and analyze your moves with an engine and against an offline database. You can also let the engine analyse a position and write the best variations to the file. If no other options are available to you or you only care about the computer analysis and less about the database moves, I would go with this.
I use Chess Openings Wizard in a way I can improve my opening knowledge. My method:
- Enter the right moves (your personal choice) in Chess Openigs Wizard.
- Do the drill-excercises to learn the moves by heart.
- Play a game (5 minutes or longer) and always check if you used your own opening repertoire. If not, drill again. If your opponent played moves that were not in your repertoire in CO Wizard you can find the best answer with the built-in chess engine.
- In this way you are constantly improving!