Is it possible to claim somehow the bitcoin "Forked Coins" if I had the BTC in my Coinbase account at the time of the forks? (besides BCH, this one was credited later).
No. It's up to Coinbase to give them to you, since they control the private keys. It seems like they won't be supporting most of the Bitcoin forks. Their position is that they
may credit fork coins at their discretion, based on the "security" and "value" of the forked network.
This is what they said about Bitcoin Gold:
We operate by the principle that our customers should benefit to the greatest extent possible from hard forks or other unexpected events. However, safety and security are also important considerations for any asset supported by Coinbase.
At this time, Coinbase cannot support Bitcoin Gold because its developers have not made the code available to the public for review. This is a major security risk.
We will continue to monitor the development of Bitcoin Gold, and if its network proves to be both secure and valuable, Coinbase may decide to support it at a later date.
Coinbase/GDAX will not sell or keep Bitcoin Gold associated with customer Bitcoin for itself. Any Bitcoin Gold will remain securely stored on Coinbase. If Coinbase were to enable support for Bitcoin Gold at a future date, customers would be able to withdraw Bitcoin Gold associated with their Coinbase/GDAX Bitcoin balances at the time of the Bitcoin Gold fork.
Is there a desktop wallet which will support the upcoming forks?
Basically, every fork has its own wallet. You should be very careful dealing with these wallets. Some of them are probably malware that are out to steal your coins. I've avoided claiming most of the forks for this reason. I don't trust the software.
