Only way to do this now if I manually open wallet that I want and I don't understand how Electrum decides what wallet to open, maybe one that last had some transaction.
It will open the last wallet that is closed.
Electrum determines which wallet file to open by checking the config located in the data directory, %appdata%/Electrum if you're using Windows. Unless you're able to edit it after every Electrum shutdown, you can't set the wallet at launch. However, you can make use of a shortcut for this. Create a shortcut for Electrum and edit its target in this format: "C:\Program Files (x86)\Electrum\electrum-4.0.9.exe" -w C:\Users\usr\AppData\Roaming\Electrum\wallets\default_wallet. You would have to specify the exact directory.
There are also limited number of addresses and change addresses shown in Addresses tab and I would like to show more of them if that is possible, and I hope I made myself clear enough.
Gap limit.
For receiving address, change gap limit like this: changegaplimit('30', 'iknowwhatimdoing')
For change address, change gap limit like this: wallet.gap_limit_for_change = 30
Both are to be entered into the console. A fair warning, you have to remember that you changed the gap limit. If you were to use addresses that were generated 21 receiving addresses ahead, you will have to change the gap limit when restoring the wallet.