This isn't hard to do if the 1000 bitcoin address is in the same wallet you can just simply send it all to your main Bitcoin address.
Sample this image below I'm going to spend/send bitcoins from my client's addresses(Bitcoin address that you give to your clients) to my main address.
https://bitcoinelectrum.com/files/2019/09/coins-tab.jpg[Electrum testnet as a sample.]
Choose the client's addresses that you want to spend or send to your main BTC address right-click and then spend.
You will be redirected to send tab on Electrum then put your main BTC address and click the max under amount and set the fee then click send.
And that's it.
But if the 1000 bitcoin addresses are not on the same wallet you have to take all private keys from all of these 1000 addresses and import it to Electrum and then go to send tab>put your main address>click the max button under amount>set the fee> then click send.
This is what it looks like on the send tab you will notice there is a new box appear below the description.
https://i.imgur.com/F7zzCCx.pngyes, i found about this electrum too yesterday.
i can generate a lot of addresses to give to the clients.
next step, should i link with blockchain api to read transaction history of each btc address?
or should i setup my own bitcoin server to do it?
but the syncing process will take a lot of time.
any opinion?